During an interview for the PBS series "Pioneers of Television," Noah Wyle said that while filming some of Carter's Africa storyline in the Kalahari Desert, the real on-set medic passed out from the heat, and Wyle (who by that time had been filmed pretending to perform hundreds of simulated medical procedures for the television show) actually inserted a real I.V. and hooked the medic up to a real saline drip.

Goran Visnjic named his own character after the writers were unable to develop an appropriately Croatian name. The character is named for Visnjic's nephew (Luka) and his best friend (Kovac).

"Dr. Greene" was the first and last two words spoken in the entire series.

The entire main cast of the first season also appeared in the fifteenth and final season: Anthony Edwards, Noah Wyle, George Clooney, Eriq La Salle, Sherry Stringfield, and Julianna Margulies.

Producers wanted the character of Carol, played by Julianna Margulies to switch from being a nurse to a doctor and even filmed episodes of her starting medical school. Margulies objected to the idea, saying that her character would be so proud of being a nurse she would never want to change, so the idea was dropped. Years later, the character of Abby, played by Maura Tierney did go from being a nurse to a doctor.

This was the most Emmy-nominated show in television history, at 123 nominations, until Game of Thrones surpassed it on 2018 adding 128.

Out of all the numerous celebrity guest stars on the show, only Sally Field and Ray Liotta have won Emmys for their roles.

Frank, the desk clerk (Troy Evans), always talks about life on the "force" as a Chicago police officer. In the first episode, he had an appearance as a police officer, who was shot and treated by the ER staff.

Carol Hathaway (Julianna Margulies) was supposed to be brain-dead from a suicide attempt in the first episode, but the character was revived for the series. For the first episode, Margulies was credited as a guest star.

If anything had gone wrong during the broadcast of the live episode, such as a technical failure or forgotten dialogue, the producers had additional actors ready to improvise a scene that would have been inserted to cover. This contingency was never used.

Season fourteen was supposed to be the final season, but the 2007-08 WGA strike left both the producers and NBC without enough episodes to provide a proper final victory lap season. They agreed to bring the show back for the fifteenth and last season, that began in September 2008, and concluded on April 2, 2009.

Matthew Watkins, the child who plays Reese Benton, Peter's deaf son, is deaf in real-life.

Dr. Chen is the only character to repeatedly call Carter by his first name.

Gloria Reuben (Jeannie Boulet), and Erik Palladino (Dave Malucci) left the show because they felt that their characters were being under-used. Kellie Martin (Lucy Knight) left the series when it became too painful to work in a medical show following the death of her sister.

Doug Ross frequently hung his head low, appearing ashamed or thoughtful or privately amused, depending on the scene. This wasn't just an element of the character: George Clooney had taken to writing his lines on papers, sheets, and other props (especially the complicated medical terminology).

The first four episodes of the show all began the same way, with one of the doctors being awakened early in the morning from "Exam 8" at the end of the hallway in this order: Greene (Pilot), Lewis (Day One), Benton (Going Home), Carter (Hit and Run). This became a recurring motif throughout the run of the series, and the 200th episode began this way as well. Of the original five doctors, Ross (George Clooney) was the only one who was never shown sleeping in Exam 8.

In the live broadcast of 1997, the baseball game that George Clooney's character is watching in the break room was the Cubs-Astros game, also being broadcast live that night on WGN.

More performers (31) received Emmy nominations as lead, supporting, or guest actors and actresses on this show, than did for any other series.

Laura Innes and Noah Wyle tied as the series' longest-appearing cast members, having appeared in thirteen out of fifteen seasons. Innes' Dr. Kerry Weaver made her first appearance in season two, stayed on as a regular until the midpoint of Season thirteen, and appeared in two season fifteen episodes. Wyle's Dr. John Carter was a regular from the start of season one, left the regular cast in the season eleven finale, had a multi-episode guest role in season twelve (for a story set in Darfur), and returned for several season fifteen episodes. Both were in the series finale, and had a few scenes together.

The character of Dr. John Carter was named after the protagonist in the classic "John Carter: Man from Mars" pulp science fiction stories. Michael Crichton, like many science fiction writers, considers it an early influence.

Although mostly shot at Warner Brother's Burbank soundstages, the cast and crew usually will make at least two trips to Chicago each season, to shoot realistic exterior scenes for several episodes, which include many familiar Chicago landmarks. These scenes are normally shot on early Sunday mornings to avoid disrupting traffic.

The basketball hoop found outside of the ambulance bay of the ER, was actually George Clooney's idea. Apparently, he liked to unwind in-between takes, by shooting some hoops. Because of this, it was placed in an area of the Warner Brothers (Burbank, California) studio lot, where it could be picked up by the camera. It quickly became a part of the series.

Michael Crichton wrote the script for the pilot episode, and it remained unchanged from when he wrote it twenty years earlier.

Julianna Margulies originally read for the part of Dr. Mark Greene's wife.

It was reported in May 2018, that within the show's release on the streaming service HULU that March, the first such service to carry all 331 episodes of the series, more than 30,000 viewers watched all 331 episodes of the series.

In "Doctor Carter, I Presume" (season three, episode one) the heard, but unseen Dr. Karubian, is played by David Schwimmer.

Noah Wyle was the last member of the original cast to leave, at the end of the 2004-2005 season. He appeared occasionally in later seasons. Sherry Stringfield is also an original cast member, but she left for five seasons, which made Noah Wyle the only cast member to be on the show every year for the series first eleven seasons.

George Clooney's cousin, Miguel Ferrer, appeared as a guest star in the two-hour pilot episode, and Clooney's aunt, Rosemary Clooney (Ferrer's mother), appeared in the second regular episode. Clooney shared scenes with neither of them.

Anthony Edwards was first choice to play the part of Dr. Mark Greene. Unfortunately, Edwards was committed to direct a feature film at the time the pilot was due to shoot, and was therefore unavailable. By sheer luck, his feature was pushed back, and he was able to film the pilot instead.

Originally planned as a film, which Steven Spielberg was supposed to direct. When plans fell through, and the project eventually became a series, Spielberg became interested in another Michael Crichton creation: Jurassic Park (1993).

From the first introduction of Dr. Kerry Weaver (Laura Innes), the character walked with a limp, and used a cane. The reason behind Weaver's disability went unexplained for many years (even to Innes--in an Ability Magazine interview, she said that the writers "wanted to keep it open, and not have it be something that was an issue"). Not until season eleven, did the show reveal that Weaver's condition was congenital hip dysplasia. But in 2006, not long before Innes left the show, the showrunners decided to have Weaver undergo surgery that would eliminate the limp and the need for the crutch. This was because Laura Innes had started to experience some real-life medical problems from her decade of playing Weaver with a limp. Innes told a reporter, "My real back was getting screwed up. I got a bone density test and the bottom of my spine is starting to curve on one side from ten years of raising my hip. . . . I've just started going to the chiropractor. I don't need an operation."

George Clooney had his first regular television role in a comedy ten years earlier called E/R (1984).

Because the show could make only a couple of location shoots in Chicago each year, the exterior scenes would often have to be filmed in advance of the rest of the episode's shoot back in Los Angeles. Sometimes a scene for an episode would have to be shot before it was even written. A famous example of this is the final scene in "Love's Labor Lost," when Dr. Greene cries on the El Train. Director Mimi Leder could only give Anthony Edwards a brief description of what was to occur and told him to "find it," "it" being the sadness Greene was experiencing.

The set for the pilot episode was a rundown hospital in East Los Angeles, as they couldn't afford to build a proper set of their own. As the rooms were quite small, this necessitated the use of the Steadicam, which has since become the trademark of the show. Real members of the public, usually punk gangs, would often pull up outside, mistaking the set for the real thing.

Noah Wyle, Laura Innes and Alex Kingston are the only main credited actors to appear with every member of the main cast at one stage or another during the show's fifteen-year run.

Glenne Headly was pregnant when she signed on to do her story arc as Dr. Abby Keaton in the third season. Originally, the writers floated the idea of writing the pregnancy into the show, but then decided that audiences would have difficulty accepting John Carter having a relationship with a heavily pregnant woman. In the later stages, Headly had to be photographed behind gurneys and in ill-fitting surgical scrubs to hide her bump.

When the show debuted in 1994, it won the People's Choice Award for "Favorite Dramatic Series" every year until 2002. It has also won the George Foster Peabody Award.

Rod Holcomb directed the pilot and the last episode of the show.

The characters of Luka and Abby lasted longer than the characters they replaced (Doug Ross and Carol Hathaway).

Some of the operations in the series were dramatized versions of real-life operations. The writers scouted out hospitals around the Los Angeles area to get ideas for new episodes. An early episode, in which a baby gets a coat hanger stuck in its throat, was based on a real emergency in a Los Angeles hospital. However, the situation was dramatized by adding a scene where the baby bleeds profusely, and required a tracheotomy (in real-life, they simply reached in and pulled the hanger out).

Due to a lack of time and money to build a set, the pilot episode of ER was filmed in the former Linda Vista Community Hospital in Los Angeles, an old facility that ceased operating as a medical center in 1990.

Throughout its fifteen-year run, the show had 26 regular cast members, nineteen of whom appeared in the final season at one point or another.

In one episode, Dr. Lewis admits that she's only familiar with the Walt Whitman poem "I Sing the Body Electric" because it appeared in song form in the movie Fame (1980). That song in that film was sung by Paul McCrane (Dr. Romano).

Including Gloria Reuben and CCH Pounder (who appeared as recurring guest stars during the first season), the original cast combined for 25 nominations in the Leading and Supporting Acting categories at the Emmy Awards from 1995-2000. Julianna Margulies (Best Supporting Actress, 1995) was the only one to ever win.

Seasons seven and fourteen are the only seasons to not have a cast change.

Anthony Edwards, Paul McCrane, Laura Innes, and Eriq La Salle are the only cast members to direct episodes throughout the shows fifteen season run.

By season thirteen, Laura Innes became the longest running cast member of the show.

The first and last episodes of the series are the only two to not air at 10:00 during the shows fifteen year run.

All original cast members who appeared in season fifteen were listed in the credits with the current stars, not as guest appearances. Alex Kingston and Laura Innes also appeared in the opening credits to the series finale due to their roles in it. In the 2009 episode guest starring George Clooney and Julianna Margulies, Noah Wyle received top billing over both of them.

In Season 8 Episode 20 "The Letter" the faxed letter from Dr Greene followed by the fax from his wife announcing his death mimics the final scene in the 1955 movie Mister Roberts. Both characters wrote nostalgic letters to their last job/assignment. Immediately after the letters are read in both scenes it is immediately followed by another letter announcing their death. Also in both scenes the reader of the letter crumples it in their hand before they announce the bad news.

After [Anthony Edwards]'s real-life wife, [Jeanine Lobell], gave birth to another baby girl, it was his call to leave the show, near the end of the 2001-02 season, to spend a lot more time with his family, in addition to pursuing other projects.

The helicopter used for this show actually belongs to the University of Chicago Hospital. It is a 1989 AEROSPATIALE SA365N-1 DAUPHIN, registration number N365UC. As of 2017, this same helicopter is still in service with the university. The registration is valid through 2019.

Dr. Carter's birth date is June 4, 1970. Noah Wyle's is June 4, 1971.

This is NBC's third longest-running drama (after Law & Order (1990) and Law & Order: Special Victims Unit (1999)), and, at fifteen seasons, it was the longest-running American primetime medical drama until 2019 when it was surpassed by Grey's Anatomy.

The character played by Ming-Na Wen was addressed only as Deborah Chen when she first appeared in the series in 1995. When she returned in 2000, she took to a more traditional name, Jing-Mei, which was also the name of the character Ming-Na played in The Joy Luck Club (1993).

The character portrayed by Leslie Bibb, Erin Harkins, was originally supposed to die in the episode where she and Luka (Goran Visnjic) were in a car accident. The producers changed their mind after the episode had been written, and after an ambiguous ending, she resurfaced a couple of episodes later, alive and well.

Alex Kingston announced in an interview in 2004 that her contract to return for an eighth year on the show was not renewed. She said she was told plots for her character had "run their course".

Mary McDonnell (Carter's Mother) was also in the sitcom E/R (1984) with George Clooney.

Vondie Curtis-Hall appeared on the show as two characters. In season one, he played a transsexual, (for which he was nominated for an Emmy) and in later episodes, he played Carla's husband, and fought Dr. Benton for custody of his son, Reese.

Sherry Stringfield is the only cast member to leave and return to the show. Ming-Na Wen had a recurring role in season one, but came back in season six.

In the episode where Dr. Romano is showing his prosthetic arm to the staff at the desk, one of the other doctors refers to him as "Robodoc". Paul McCrane played one of the bad guys in RoboCop (1987).

Abby is the only character to have been both a nurse and a doctor.

In 2007, this show tied with Cheers (1982) for being the most Emmy-nominated show ever with 117 nominations.

Casting Director John Frank Levey originally suggested Michael Beach for the role of Dr. Peter Benton. John Wells felt Beach didn't complete the ensemble, and chose Eriq La Salle instead. Beach eventually appeared on ER as Al Boulet. Beach would also later be cast as a regular in Third Watch (1999), another Wells-produced series.

The first six DVD box sets of ER are unusual in the fact that they are all in anamorphic widescreen, even though these episodes were broadcast in a standard 4:3 format. Only the live episode "Ambush" is not in the widescreen format.

In the novel written by Michael Crichton, Dr. Lewis is a man, and Dr. Benton is not African-American.

Lieutenant Sandy Lopez (Lisa Vidal) was the first lesbian Latina primary or secondary character on a television series.

The first person to appear on-screen in the first episode is Dr. Mark Greene (Anthony Edwards).

Maura Tierney (Abby Lockhart) & Julianna Margulies (Carol Hathaway) also worked together on the fourth season of The Good Wife (2009).

Sissy Spacek was originally cast as Dr. Weaver's mother, but was eventually played by Frances Fisher in episode "Just as I Am" (2005).

Michael Crichton's original script took place in Boston Memorial Hospital. Dr. Mark Greene was "Richie Greene" in this version, and Dr. Susan Lewis was "Beth Lewis."

Staff seem to invariably pronounce the last name of Luka Kovac like "KOH-vahtch," whereas his own pronunciation of it is more like it rhymes with Dutch. Bear in mind that Goran Visnjic who plays the role is a native Croat and speaker of Croatian, just like the character.

Dr John 'Tag' Taglieri & Dr Greene both starred in Top Gun together as 'Slider' & 'Goose' along with Dr. Swift as 'Jester'.

After the show premiered on September 19, 1994, it aired on Thursday nights at 10:00 for its entire run.

Dr. Romano (Paul McCrane) has a model of an Apollo Saturn V rocket in the background of his office. McCrane played astronaut Pete Conrad, commander of Apollo 12, in the HBO mini-series From the Earth to the Moon (1998).

Todd Allen auditioned for the role of Dr. Mark Greene, but instead appeared in a different pilot that season, Frogmen (1994), which remained unaired, due to it starring O.J. Simpson, and coinciding with his murder trial.

Because the original credits were abandoned in season thirteen, neither Maura Tierney or Parminder Nagra were seen with the "Starring" moniker attached to their name, although they were each the lead roles for a time. John Stamos, Angela Bassett, and David Lyons were depicted in the opening credits just once, when the original style was brought back for the series finale.

The Los Angeles hospital, Linda Vista Community Hospital used for interior shots is ironically located on South Chicago St., which is where the show's hospital is located.

Anthony Edwards (Mark Greene) and John Cullum who played his dad (David Greene) both starred in the TV series Northern Exposure.

Carter's full name is John Truman Carter III.

Tony Todd was considered for the role of Dr. Peter Benton.

In the whole series of this show the main bathroom thats near curtain area 3 and down the hall from trauma 2, they use the bathroom for men and women. One episode it will be for women and the next episode it will be for men.

When the series debuted, [Laura Innes] was to play the character of [George Clooney]'s girlfriend, when plans were scrapped. The following year, she tried again, this time to test the part of Dr. Kerry Weaver. Originally intended to be a guest-star, she appeared for 8 episodes, and became a regular for the third season.

Lisa Zane tested for the part of Dr. Susan Lewis. She would later play a love interest for George Clooney's character.

Whenever the series would show sequences involving local TV news the station used was always WMAQ, the NBC owned and operated station in Chicago.

After Laura Innes left the show in January 2007, NBC received some pressure from GLAAD to introduce more LGBT characters.

George Clooney's character was originally going to be called Tom Ross, and Julianna Margulies was going to be called Barb Hathaway.

Troy Evans, who would later play desk clerk Frank Martin, appeared in the pilot as a character referred to as Officer Martin. In scripts, the first name was Jonathan. There was never any indication given in the show if this is the same character, and as of the series finale, producers would not speculate either.

Several actors who would later star on CSI appeared on ER. George Eads, Jorja Fox, Marg Helgenberger, Liz Vassey and Wallace Langham. Additionally, ER cast members Alex Kingston, Paul McCrane and Sherry Stringfield would later guest star on CSI .

Abby's full name is Abigail Marjorie Wyczenski Lockhart.

One of Executive Producer Steven Spielberg's favorite films is Lawrence of Arabia (1962). The cast of this series has included Alex Kingston, whose ex-husband Ralph Fiennes played Lawrence in A Dangerous Man: Lawrence After Arabia (1992). Also appearing on the series were Miguel Ferrer, Rosemary Clooney and George Clooney, the son, ex-wife and nephew, respectively, of Lawrence of Arabia (1962) cast member José Ferrer.

Dr. Ray Barnett's band is called "Skunk Hollow".

Justina Machado makes a guest appearance here as the sister of a gangbanger. She would return to the series eleven years later in its final season to play the girlfriend of Dr. Archie Morris.

Doctors Mark Green and Elizabeth Corday lived at 1211 Dupont Drive.

Linda Cardellini (Samantha Taggart) & John Leguizamo (Dr. Victor Clemente) also worked together on Bloodline (2015) as Meg Rayburn & Ozzy Delvecchio respectively.

Michael Gross and Fred Ward portray the fathers of John Carter and Abby Lockhart respectively. The two appear together as Burt Gummer and Earl Bassett in "Tremors" (1990) and "Tremors 2: Aftershocks" (1996).

Cress Williams & Jason George played Miranda Bailey's first & second husbands on Grey's Anatomy. They also both had recurring roles on ER. Cress Williams as Jeanne Boulet's husband and Jason George as a love interest for Sam (Linda Cardellini). They both appear in the episode Status Quo (season 14; episode 11). This episode was while Williams was on Grey's. (January 3, 2008).

Julianna Margulies (Carol Hathaway) & John Cullum (David Greene) also worked together on episode 4.18, The Good Wife: Death of a Client (2013), as Alicia Florrick & Cardinal James respectively.

Troy Evans (Frank Martin) was a police officer in E.R initally before becoming the desk clerk. He also played a police officer in Halloween 5: The Revenge of Michael Myers (1989), which was also set in Illinois. Chicago in E.R., and Haddonfield in Halloween, respectively.

Abby's middle name is Marjorie.

Members of the cast often use medical jargon during the ER scenes. For instance the oft used term EPI is short for epinephrine. A steroid often used to jump start the cardiovascular system once it's stopped or slowed down. Or V-TACH, which is short for ventricular tachycardia, meaning, essentially the heart is pumping in reverse during a heart attack.

With the exception of Mark Greene's daughter Rachel, and Kerry Weaver's son Henry, all of the children born to main characters were unexpected pregnancies.