According to exec producers Danny Bilson and Paul De Meo in their DVD commentary, if the show was picked up for a second season, the premiere would have featured the Trickster, Captain Cold, and Mirror Master teaming up to take on the Flash.
When Christina McGee calls Barry for the first time, she tells him to come to "50, Garrick Ave". Jay Garrick was the name of the first Flash, and the series premiered in the year of his fiftieth anniversary of publication.
Mark Hamill would reprise his role of James Jesse AKA 'The Trickster' in The Flash (2014) in the episodes 'Tricksters' and "Running to Stand Still".
When Jay gives the press conference, he is asked a question by a reporter who identifies herself as "Linda Park". Linda Park is the TV reporter girlfriend and later wife of Wally West, the third Flash.
Each episode was budgeted at $1.5 million, then the largest budget ever for a series.
The show was canceled because of high production costs and a fluctuating time-slot which caused poor ratings.
The series is replete with references to the comic books and their creators. In addition to the "Garrick Ave." reference mentioned in another item, episodes have referenced "The Hotel Infantino" (a nod to Silver Age Flash co-creator Carmine Infantino), "police captain Julius Schwartz" (a nod to Silver Age Flash co-creator Julius Schwartz), "the intersection of Gardner and Fox" (a nod to Golden Age Flash creator Gardner Fox), "Professor Zoom" (a recurring villain in the Silver Age Flash stories) and "Gorilla Grodd" (another recurring Silver Age Flash villain).
John Wesley Shipp later did the voice of Professor Zoom, an evil speedster and The Flash's arch enemy in Batman: The Brave and the Bold: Requiem for a Scarlet Speedster! (2010).
According to producers, had the series received a second season it would have featured appearances by classic Flash villains Vandal Savage and Weather Wizard.
Danny Elfman composed the theme for "The Flash", as well as Batman: The Animated Series (1992). The music is exceptionally similar between the two shows.
The Flash is not one, but three characters from DC Comics, and all three of them managed to make it into the series in some way. Jay Garrick, who was the first Flash and whose adventures inspired Barry Allen (the second) lives on in the name of Barry's brother, whose death inspires our hero. Barry Allen was a police scientist, but was also married to Iris West, the aunt of Wally West (the third Flash) who briefly dated Tina McGee some time after Barry died. The Flash of the television series is a combination of Barry Allen's name and day job with Wally West's social life, and a personality falling somewhere between the two.
The series had a hard time attracting ratings as it first aired on Thursdays at 8 against The Cosby Show (1984) and The Simpsons (1989), who were having a highly hyped ratings duel. CBS moved the series to 8:30, an unusual time slot for a hour long drama and aired a promotional campaign to remind viewers to switch over "After Bill, After Bart." The move didn't work, and the series was relegated to Saturday, and eventually in a last ditch effort to try to build interest for a possible second season was moved to Friday.
John Wesley Shipp who played The Flash in 1990 - 1991 and Grant Gustin who played The Flash in 2014 - Present were both born in Norfolk, VA.
The role of Barry Allen/The Flash was originally written for Richard Burgi. Burgi ended up guest starring as Deadly Nightshade in The Flash: Deadly Nightshade (1991).
In The Flash (2014) episode Tricksters the Trickster (portayed by Mark Hamill) kidnaps Barry Allen's father Henry Allen (portrayed by John Wesley Shipp) mirroring Shipp's and Hamill's portrayals as The Flash and Trickster respectively in the 1990 series.