Oliver Queen has an occasional "tic" described by Stephen Amell as a sort of anxiousness when Oliver wishes he was holding his bow.
Oliver is once seen wearing a prison shirt with the number 399471 on the pocket. This is the hex code for the shade of green of his hood.
John Diggle was created specifically for this series, and was added to the mainstream DC universe starting with the New 52 titles, introduced in "Green Arrow" Issue 24, October 2013. He joins Chloe Sullivan (Allison Mack) from Smallville (2001).
The Queen Mansion exterior shots are filmed at the Hatley Castle in the Hatley Park National Historic Site located in Colwood, British Columbia. This is the same Castle used for the Luthor Mansion exterior shots in Smallville (2001), and for Professor Xavier's castle in the X-Men (2000) film series. The location is also used in Deadpool (2016).
This is the second time Brandon Routh portrays a superhero, here he stars as Ray Palmer/the Atom after starring as Clark Kent/Superman in Superman Returns (2006).
Felicity Smoak (played by Emily Bett Rickards) was only supposed to be in one episode (Arrow: Lone Gunmen (2012)). However, the positive reaction to her led to her becoming the main character.
Although Oliver's transformation into The Arrow differs from the original DC comics storyline, it's not very far off. In the comics, Oliver had a fascination with bows and arrows from a young age, and always had one with him. When he was a young teen, both of his parents were killed. (He was also an only child) When he was 16, he was traveling by sea when his boat crashed and he was marooned on an island with nothing but his bow to aid in his survival. He taught himself to hunt and perfected what little archery skills he had. He grew to be a man and stumbled upon the illegal trafficking of the criminal China White. After putting a stop to her operation, he found his calling as a crime fighter and "borrowing from Bruce Wayne's book" returned home to Star City as the Green Arrow.
Sin often calls Roy Harper by the nickname "Abercrombie", Colton Haynes who plays Roy was a model for Abercrombie and Fitch before becoming an actor.
Coast City is mentioned sporadically throughout the series. In the comics, Coast City is the home of Hal Jordan, the Silver Age Green Lantern.
In the comics, Deathstroke (aka Slade Wilson) is an anti-hero with enhanced or peak strength, speed, stamina, and reflexes (sometimes bordering on superhuman levels). He's tactically brilliant and adept at turning an opponent's own abilities against them. He has defeated Batman and Nightwing in combat, and he has given even Wonder Woman a run for her money in a fight.
In almost every episode the title of that episode is said by someone at some point.
Midway into Season 2, the character of scientist Barry Allen is introduced. Soon after his debut he suffers a classic comic book "freak accident" and becomes 'The Flash' in his own TV series The Flash (2014), which would go on to crossover with Arrow a number of times.
On numerous occasions the city of Blüdhaven is mentioned, and even visited once. In DC comics, Blüdhaven is a city under the protection of Dick Grayson, AKA Nightwing.
Each time Oliver revealed his secret, someone's life was in danger (usually, but not always, his own): When Diggle found out, Deadshot had tagged him with a curare laced bullet. When Felicity found out, Oliver had just been shot by his mother. When Barry Allen found out, Oliver had been poisoned. When Tommy found out, Malcolm Merlyn was dying from a gunshot wound. When Merlyn himself found out, he was seconds away from killing Oliver. When Roy found out, another earthquake machine was about to go off and the revelation shocked Roy out of his mirakuru rage long enough to help disarm it. The exceptions to this being Laurel, Moira and Thea and his new Team Arrow (Season 5).
Malcolm Merlyn is called "Al Sa Her" by Nyssa, which is Arabic for The Magician. Merlyn the Magician is a famous wizard in the legend of King Arthur, and is also a DC comic book character.
Laurel trains with Ted Grant as she prepares to become Black Canary. In the comics, Ted Grant is the JSA hero Wildcat who was a mentor to Dinah (Laurel) Lance.
The name of Oliver's club is Verdant, meaning "of bright green colour" and the large V above it is reminiscent of an arrow. Together these are a subtle nod to the DC Comics character.
Instead of Brandon Routh playing Ray Palmer (The Atom) the producers originally planned for him to play Ted Kord (Blue Beetle). But CW didn't have the rights to use him so they made the part for The Atom.
Ivo's freighter was named, "Amazo." In DC comics, Amazo was the name of Ivo's greatest invention; an android that could absorb and store the super powers of any meta-being.
When Barry, Cisco and Caitlin appear in a scene, the theme from The Flash (2014) can often be heard.
In the comics the real name of Starling City is Star City. The name Star City is used in later seasons (some characters keep forgetting and correct themselves).
Curare is a real paralytic/muscle relaxant that is sometimes used on arrowheads to hunt animals but is mainly used by physicians as an anesthetic. In high enough doses, it can cause respiratory failure and cardiac arrest.
Live-action debut of Ra's al Ghul's Nyssa, who in the comics is known as Nyssa Raatko.
The arrowhead design of the title logo has changed every season. Season 1 had a flat arrowhead shape. Season 2 retained the same shape of the arrowhead as season 1, only dimensions were added to it. Season 3 is a completely different arrowhead shape design complete with engraved symbols. A few instances in Season 3 the logo changed to reflect the storyline. In Arrow: Draw Back Your Bow (2014), the title arrowhead logo was that of Cupid's heart shape arrow. In Arrow: The Brave and the Bold (2014), lightning was added to the logo as The Flash guest starred. In Arrow: The Return (2015), the arrowhead logo reverted to the season 2 arrowhead when Slade Wilson returned. In season 4, the arrowhead has a bright green color. In season 5, it has a bright green color similar to season 4's, but bevelled with an inverted Y-shape at the bottom.
The exterior shot of the police headquarters is actually the main branch of the Los Angeles Public Library.
Throughout the show there is a special theme soundtrack that plays whenever Malcolm Merlyn or the dark archer (John Barrowman) is on the scene. It's first heard during the revelation of the dark archer as Malcolm in Arrow: Year's End (2012), towards the end of Arrow: State v. Queen (2013) and in Arrow: The Magician (2014).
As of season 4, John Barrowman (Malcolm Merlyn) is the oldest of the main cast members and Emily Bett Rickards (Felicity Smoak) is the youngest. Though Willa Holland (Thea Queen) is only about a month older than Rickards.
During an episode on season 1, Oliver says this to Dig: "...you know us billionaire vigilantes... We do love our toys." This is a reference to one of the most known DC characters, Batman.
The first depiction of the League of Assassins using the name from the comics. In Batman Begins (2005), the group was renamed League of Shadows.
The Starling City skyline is actually footage from various cities including Frankfurt, Germany, Center City Philadelphia, PA, Back Bay Boston, MA, Tokyo, Japan, and Singapore.
The name Isabel Rochev is listed two names down from Adam Hunt (the primary antagonist of the pilot episode) in Oliver's book of names. Isabel Rochev is eventually a reoccurring character played by Summer Glau in season two.
Oliver had mainly two teachers that were responsible for giving him the skills that he uses as The Arrow. Slade Wilson (a.k.a. Deathstroke) who taught him hand to hand combat and melee weapons training and Shado who taught him the bow. Originally in DC comics, Oliver taught himself archery and was taught martial arts by Natas, who was Deathstroke's mentor. In season 5 it is revealed that Oliver had one more mentor in Talia Al Ghul who furthered his martial arts training and inspired the Arrow persona.
In DC comics Roy Harper eventually lost an arm and took a bionic arm substitute; appropriately dubbing himself "Arsenal." Also, DC supervillain Solomon Grundy's real name is Cyrus Gold who appears in season 2 of the series.
Stephen Amell was the very first of a thousand actors to audition for the title role, as were Grant Gustin for The Flash (2014) and Melissa Benoist for Supergirl (2015).
Alex Kingston and John Barrowman both starred as companions to The Doctor in the BBC's Doctor Who (2005). Kingston starred as River Song and Barrowman as Captain Jack. Colin Salmon also appeared as Dr. Moon in two episodes of Doctor Who (also the first appearance of River Song).
The character of John Diggle was rumored by fans to eventually become either the Green Lantern, or the Guardian. However, Diggle ultimately assumed the identity of Spartan and the Guardian mantle was taken up by Jimmy Olsen in "Supergirl."
Jacqueline MacInnes Wood portrayed Sara Lance in the first season. She was recast in the second season with Caity Lotz.
In Arrow: The Brave and the Bold (2014), when Oliver is introducing Barry Allen to Captain Lance, Lance mistakes his name as Bart Allen. In the comics, Bart Allen is Barry's grandson, who is the sidekick of the second Flash and then eventually becomes the Flash himself.
Stephen Amell also wanted to appear in the DC Extended Universe films. Promotional material for Batman v Superman: Dawn of Justice (2016) indicated that Oliver Queen does exist in that universe.
Andrew Kreisberg originally stated that the series is a more realistic take on the character in comparison to the source comic books. Oliver is the only masked vigilante in the world, "there are no aliens and there are no super-villains". This held up more or less, until the decision was made to add the Flash into the equation, which changed everything.
Felicity Smoak originated as the step-mother of the superhero Firestorm (Ronnie Raymond) in the pre-New 52 continuity in the "The Fury of Firestorm" comics. Later due to her popularity on the show she was re-introduced in the New 52 continuity as part of the "Green Arrow" comics starting with Issue 35 that was released in October 2014. Also for the New 52 version, her appearance is based on Emily Bett Rickards' portrayal of her on the show.
Brandon Routh's character Ray Palmer is revealed to be another DC hero, Atom. In the comics, he, along with Green Arrow (Oliver Queen), Black Canary (Dinah Laurel Lance) and The Flash (Barry Allen), is a member of the Justice League of America.
John Diggle was named after Andy Diggle, writer of "Green Arrow - Year One". A "judge Grell" is referenced in the pilot, paying homage to Michael Grell, the long running writer of the Green Arrow comics.
In season 3 Malcolm makes a reference towards a company called Ferris Air. This is the company for which Hal Jordan (Green Lantern) has been known to fly for.
The nursery rhyme for Cyrus Gold (Solomon Grundy) is: Solomon Grundy, Born on a Monday, Christened on Tuesday, Married on Wednesday, Took ill on Thursday, Grew worse on Friday, Died on Saturday, Buried on Sunday. That was the end, Of Solomon Grundy. The rhyme has been used in the movie The Accountant (2016).
John Barrowman (Malcolm Merlyn), Alex Kingston (Dinah Lance) and Colin Salmon (Walter Steele) have all appeared in Doctor Who.
Every season the first episode opens up with Oliver running through a forest or some kind of foliage. In seasons 1 and 2 the opening shot is of Oliver running through the forests of Lian Yu. In season 3 it is a line of trees and bushes along a train route. In season 4 he is jogging through a park near his and Felicity's home.
The shots showing the Queen Consolidated Towers are stock footage of the real life Belgacom Towers set in Brussels, Belgium. The Q-Consolidated logo was added in post production.
Originally intended to follow a more realistic take without meta-humans as influenced by Christopher Nolan's The Dark Knight (2008) trilogy. This changed with the introduction of The Flash (2014).
For Green Arrow's first two plus decades, he was a relatively minor superhero character, without his own comic book series. In 1969, the character lost his millions and began co-starring in Green Lantern's series. He became more of an earthy people's hero, and was quite popular throughout the 1970's, both with Green Lantern, and as part of DC's Justice League of America.
In the comics, Green Arrow had bright blond hair and wore a small mask to hide his identity. Also prior to the New 52 relaunch he had a prominent bright blond goatee, and first wore a Robin Hood style hat, later with no hat, where instead he used a hood. But in the television show, much like his New 52 counterpart, Arrow wears only a green hood (deep and large enough to always cover his face in shadow) and there is no goatee, only stubble. Also instead of a mask he wore some green face paint around his eyes that looks similar to his comic book mask to hide his identity (until the events of Season 2's Three Ghosts where he receives a proper mask), and although he is blond, it is more dark or dirty blond.
Katie Cassidy went to prom with Tyler Hoechlin who plays Superman on Supergirl (2015).
Nick E. Tarabay, Katrina Law, Manu Bennett and Cynthia Addai-Robinson all portrayed leading characters in both Arrow and Spartacus: War of the Damned (2010). Liam McIntyre (who portrayed the titular character in Spartacus) went on to play Weather Wizard, a supervillain on The Flash (2014).
In the comics, Roy Harper has a few superhero monikers, the first of which was Speedy. Though in the series the name belongs to Thea, Roy is referred to by this name at least twice and a couple of times as "Red Arrow", which was his second moniker. Ultimately, Roy takes the name Arsenal which also ties to comic lore.
In Arrow: The Secret Origin of Felicity Smoak (2014), the t-shirt that Cooper wears is a reference to the very first "Justice League" comic book.
Both Stephen Amell from Arrow and Grant Gustin from The Flash (2014) played guest roles on the TV show 90210 (2008).
Both Stephen Amell and Emily Bett Rickards are Canadian. Amell was born in Toronto while Rickards was born in Vancouver.
The show is notorious for the frequent shirtless scenes of lead star Stephen Amell. The pilot contained an intense and lengthy workout sequence with Amell shirtless that went viral. Such was the Internet buzz created by Amell's superhero physique that the producers added numerous shirtless scenes to nearly every episode of the first Season. Creator and show-runner Marc Guggenheim called this strategy "absposition" - dumping huge chunks of exposition on the audience while Amell shows of his abs. Amell's abs also became the focus of all marketing and promotion as he was always featured shirtless on the posters and all promo material, stills and trailers always contained shots of Amell shirtless. While admitting that it required a huge effort for him, Amell said he had no problem in flaunting his physique because it contributed to the show's popularity. He said, "Me being shirtless isn't the only element that's made it successful, but it is certainly part of the total equation and I'd be silly to think that it is not." While at Comic-con 2014 to promote the upcoming season of the show, he famously lifted his shirt to show off his abs to the audience getting thunderous applause from the packed auditorium Hall H. The show-runners have also acknowledged the huge popularity of Amell's shirtless scenes and vowed that the show will feature such scenes throughout its run.
John Diggle's deceased brother is named Andy, as a tribute to Andy Diggle. Andy Diggle is a writer credited with writing the 2007 limited comic series Green Arrow: Year One. This limited series would come to inspire the creation of the TV series. Andy Diggle also worked on successful series such as Swamp Thing, Thunderbolts, and Daredevil.
As of season 5, the penultimate episodes of the seasons have been named after Bruce Springsteen songs: Arrow: Darkness on the Edge of Town (2013), Arrow: Streets of Fire (2014), Arrow: This Is Your Sword (2015), and Arrow: Lost in the Flood (2016). Season 5 penultimate episode is named Missing.
A reference to Blüdhaven (the city that is home to the hero Nightwing) is made in season 2 by Roy.
Some actors from the TV series Spartacus: War of the Damned (2010) appear in the series in recurring roles. Stephen Amell was considered to take over the role of Spartacus from Andy Whitfield, before Liam McIntyre was chosen to take over the role. McIntyre would later be cast as The Weather Wizard on the spin off The Flash (2014).
On this show John Barrowman and Colin Donnell play father and son, respectively, whereas in real life they're just about 14 years apart.
Both Katie Cassidy and Stephen Amell had minor roles in Season 1 of Fox's New Girl (2011). Cassidy played Brooke, a girl Schmidt and Nick knew in college, while Amell played Kyle, Cece's boyfriend.
Stephen Amell joined forces with Neville against Stardust and King Barrett for a match in the WWE Summer Slam. He was rumored to wear the iconic Green Arrow suit in the ring during battle.
Colin Donnell (Tommy Merlyn) and John Barrowman (Malcolm Merlyn) both played Billy Crocker in revivals of Anything Goes. Barrowman in 1989 and again in 2003. And, Donnell in 2011.
Oliver Queen's mother is named Moira Queen. In Smallville (2001), his mother is named Laura, but his mother-in-law is Moira Sullivan.
Caity Lotz wears a clear blond wig when she portrays The Canary to ensure the contrast between the black leather suit and her hair.
Nick E. Tarabay is the first actor from Spartacus: War of the Damned (2010) to portray Captain Boomerang in the series. His co-star Jai Courtney will portray the character in the upcoming film Suicide Squad (2016), along with handful of his other Spartacus co-stars appear in the Arrow/Flash television universe.
Edward Fyers is a recurring nemesis for Oliver Queen on the island. In the comic book series sometime after "The Longbow Hunters", Edward Fyres became a recurring nemesis for Green Arrow. Fyres in the comic book was a mercenary, not unlike the character in "Arrow".
Episode no.8 of every season(except the first) has been a crossover episode.[ Season 2: The Scientist (The Flash) Season 3: The Brave and the Bold (The Flash) Season 4: Legends of Yesterday( Legends of Tomorrow & The Flash) Season 5: Invasion! (Legends of Tomorrow, The Flash, and Supergirl) Season 6: Crisis on Earth-X, part 2 (Legends of Tomorrow, The Flash, and Supergirl)]
In the comics, Oliver Queen is known for sporting a trademark goatee. Stephen Amell reportedly allowed his beard to grow during the Season 2 hiatus and fashioned a goatee while shaving it and "looked like someone with a record trying to blend into a new city." When asked if his version would ever use the goatee, he tweeted "100% no. Never. Our show could go 14 seasons and a goatee will never appear. Hope that clears things up. Forever." An older Oliver, however, does sport the goatee in Legends of Tomorrow (2016), based on Frank Miller's "The Dark Knight Returns".
The Green Arrow costume was designed by Colleen Atwood, who also designed the The Flash (2014) and Supergirl (2015) costumes.
As she becomes Black Canary, Laurel uses a blond wig over the civilian brunette hair. In Smallville (2001), the opposite happened as she used a brunette wig over her blond hair, for her civilian look.
In Arrow: Streets of Fire (2014), Detective Lance radios in to the police station saying Delta Charlie 52. An Easter egg referring to DC's Comic book series, The New 52.
Sara Lance's hero persona was dubbed simply "The Canary" and other than sharing the black suit, she is not actually the persona of Black Canary from DC comics. When Laurel takes up the Canary mantle and the name Black Canary, she more closely fulfills her comic book counterpart's role.
The Queen Mansion exterior shots are filmed at the Hatley Castle in the Hatley Park National Historic Site located in Colwood, British Columbia. This is the same Castle used for the Luthor Mansion exterior shots in Smallville (2001), another DC Comics origin story distributed by Warner Brothers and for Professor Xavier's castle in X-Men 2 (2003) and X-Men: The Last Stand (2006).
At one point, Malcolm Merlyn shares his opinion about naming the new vigilante "Green Arrow" just before Oliver Queen replies by saying, "Lame."
Sara Lance (the first Canary on the show) is loosely based on Dinah Drake; the first Black Canary in the comics. Like her comic book counterpart, she was mainly a very skilled martial artist and did not possess the "Canary's cry."
In the comics, Oliver Queen's birthday is on the 9th of December whereas in the series it differs to May.
Laurel's hair started off as dark brown in season 1 and got a little lighter each season until season 4 when it's completely blonde. This is in reference to the comics where Dinah Lance's hair is black, but as the Black Canary, it's blonde.
Although they portray American characters, Paul Blackthorne and Alex Kingston are both English. Katrina Law who portrays Nyssa with an English accent, is American.
Dylan Neal (Dr. Anthony Ivo) portrayed Ray Sachs in Smallville (2001), also based on DC Comics characters - and also featuring Oliver Queen, the Green Arrow.
Shado, Oliver, and Slade were stranded in Lian Yu, leaving their initials to be SOS.
During many events in the show, Quentin Lance reports crimes as DC-52. This refers to the New 52
In season three, Felicity Smoak reveals her age to be 25, making her character's birth year around 1989. However, the actress that portrays her, Emily Bett Rickards, was born in July 1991. Conversely, Thea Queen's character was born in 1995. However, Willa Holland, the actress playing her, was born in June 1991. She is a month older than Rickards.
In Arrow: Taken (2016), Oliver said that he and Mari had an "animated adventure last year". It is the literal truth because most of the Arrow cast provided the voices for their characters in the animated Vixen (2015). Also Grant Gustin and Carlos Valdes from The Flash (2014) stood for their animated characters' voices in Vixen.
Paul Blackthorne (Det. Quentin Lance) has acted in Bollywood movie "Lagaan". In fact it was his first film. He played the character of Captain Andrew Russell. Also the movie was nominated for Oscars.
The character Shado is based on the femme-fatale with the same name from DC comics. Unlike her onscreen counter part, (who was the daughter of a Chinese soldier and Oliver's archery teacher) Shado was the daughter of a prominent Yakusa (Japanese Mob) agent. She made a career fighting for them and her activities brought her into Oliver's sights after he had become Green Arrow. Shado once tended to a wounded Oliver but copulated with him during his recovery and became pregnant with his first son Robert. In the New 52, Shado was instead retconned as the former lover of Oliver's father Robert and the mother of Emiko, who is Oliver's half-sister.
Lyla Michaels, of Task Force X, uses the code name Harbinger. Lyla Michaels was a character who aided the Monitor in DC Comics seminal maxi-series, Crisis on Infinite Earths (though both debuted earlier). Lyla is infused with powers and renamed Harbinger.
David Ramsey (Diggle) and Stephen Amell (Oliver) both portray vigilantes, as well as mayors. David portrays the mayor in the series Blue Bloods (2010).
Two episodes coincidentally share the same name as some Once Upon a Time (2011) episodes: Arrow: Darkness on the Edge of Town (2013) // Once Upon a Time: Darkness on the Edge of Town (2015). And Arrow: The Return (2015) // Once Upon a Time: The Return (2012).
In DC Comics, Slade Wilson's full mercenary title was "Deathstroke: The Terminator." In this series, he is solely referred to as "Deathstroke."
Neal McDonough who plays Damien Darhk, has played Green Arrow in many animated tv shows and movies.
Neal McDonough (Damien Darhk) voiced the Flash in the video game "Injustice: Gods Among Us", and also the Green Arrow in the animated short DC Showcase Original Shorts Collection (2010).
Live-action debut of several DC Comics characters such as Felicity Smoak, Cupid, Katana, Ted Grant/Wildcat, Vixen, Roy Harper, Bill Wintergreen and many others.
Neal McDonough, as Damien Dhark, who kidnaps Oliver's son named William. In season 9 of X Files, his character Robert Cromer tries to kill Mulder & Scully's son William.
Willa Holland was publicly upset this series' version of the Suicide Squad was "killed off" in favor of Suicide Squad (2016). According to her, the showrunners "had to axe all of the characters before we even got to show them, which was very annoying".
Arrow and its spinoff The Flash have had many crossovers throughout their seasons. There have been moments where characters from The Flash and Arrow go to the others city without seeing the main character. Barry had crossed over to the show Supergirl a few times by jumping through the multiverse.
Katie Cassidy actually participated in the creation of the Black Canary costume. According to her, a reason it fully covers her body is that Caity Lotz would often freeze while filming scenes in the cold in her Canary costume.
The exterior of the Starling City Police department building is the same as the one in the Martin Lawrence comedy movie Blue Streak (1999).
Neal McDonough who plays Damien Darhk in season 4 of Arrow also voiced Floyd Lawton (Deadshot) in Batman: Assault on Arkham (2014).
Both actresses who plays the Lance sisters have the name Katie, even though the actress who plays Sara is spelled Caity, but is pronounced the same.
Rutina Wesley is the fifth actor from True Blood (2008) to star in a comic book superhero adaptation. Anna Paquin was in the X-Men films, Kevin Alejandro in Arrow (2012), Joe Manganiello in Spider-Man (2002) and Deborah Ann Woll in Daredevil (2015).
The character Roy Harper (Speedy) also appears as a main character in the animated show "Young Justice" that ran on Cartoon Network but was canceled after 2 seasons. Oliver attempted to call him Speedy, to which Roy objected. Thea later adopted the name of Speedy; Roy settled on the name "Arsenal".
Katie Cassidy (Black Canary) was in the cast in the short-lived CW series, Melrose Place (2009), where her co-star, Jessica Lucas, also portrays another DC comic-book character in Gotham (2014) as Tigress/Tabitha Galavan.
Originally Emily Bett Rickards (Felicity Smoak) was only supposed to appear in three episodes. However, due to her chemistry with Stephen Amell (Oliver Queen) she became a regular character in the show.
While Thea Queen was initially an original character in the show (especially since Oliver was originally an only child in the comics) her inclusion in the series would lead to the creation of Emiko Queen in the comics during DC's New 52 event. Emiko like Thea is also Oliver's half-sister due to also being the illegitimate child of Oliver's father Robert and Shado). These characters would end up having a number of things in common, including being trained and used as an assassin by their other parent (Malcolm Merlyn for Thea and Shado for Emiko) and both would end up turning against them and joining their brothers' team. One of the code-names that Thea considered "Red Arrow" would end up becoming Emiko's code-name when she adapted her own superhero identity during the DC Rebirth event.
Stephen Amell (Oliver Queen / Green Arrow) is the only actor to appear in every episode of the series.
In season 1, episode 18, Salvation, Laurel's (Katie Cassidy) mother, Dinah (Alex Kingston), says "I'm off to Central City, I'm sure I'll be home in a flash." That is a direct reference to The Flash/Barry Allen, (Grant Gustin) who was brought into the show a year later in the second season. A year after that, Barry was struck by lightning in the new hit series The Flash (2014). Every year the Flash/Barry Allen was referenced or introduced until he got his own show.
Though Laurel is meant to be a few years older than Sara, Katie Cassidy is only about a month older than Caity Lotz.
Stephen Amell was the very first of a thousand actors to be tested for the title role of Oliver Queen/Green Arrow, as were Grant Gustin for The Flash (2014) and Melissa Benoist for Supergirl (2015).
In season 6 this became the first CW show to name drop Bruce Wayne, hinting at a appearance of Batman later in the sixth season.
In episode 4, season 3 Nyssa states that by initiating The Undertaking (season 1) Merlin broke the rules of the League of Assassins. The Undertaking's purpose was to cleanse the city of its corrupt and criminal element, this was the same goal as Raz al Ghul (Nyssa's father and the leader of the League) had for destroying Gotham in Batman Begins (2005). Evidently this rule doesn't exist in the "Nolanverse".
During Arrow: Dodger (2013), Baltimore City is displayed. You can clearly see the inner harbor and the John's Hopkins tower.
Neal McDonough, who plays Damien Darhk, portrayed the Green Arrow in a short film in 2010.
The news channel News 52 is shown many times on the Arrow. This is a nod to the DC comics 2011 reboot New 52.
A still of Juliana Harkavy testing Dinah Drake's new Black Canary costume leaked online before Season 6 started.
The Star City skyline is actually Boston, Massachusetts and the clock tower is The Custom House.
In the dream world during the Invasion crossover, Malcolm Meryln says that his son, Tommy, is a doctor in Chicago. Colin Donnell, who plays Tommy, also played as a doctor in the series "Chicago Med".
Barthon Mathis (Michael Eklund) is one of two Arrowverse characters that have become the Dollmaker in the comics. The other is Winn Schott (Jeremy Jordan) in Supergirl (2015), even though he is originally named Anton Schott.
Although the character of Robert Queen was born in 1958, the actor who portrays him, Jamey Sheridan was born in 1951.