A 20-year-old script from the author of Jurassic Park led to the creation of one of the most highly regarded and longest-running dramas in television history, and launched the careers of George Clooney and Julianna Margulies in the process. Here are some facts about ER that have been properly sanitized.

1. IT BEGAN AS A MICHAEL CRICHTON MOVIE SCRIPT.

It was about 180 pages long and featured more than 100 characters. Crichton was a medical student at Harvard Medical School in the 1960s, and John Carter was the stand-in for Crichton. Steven Spielberg was an executive producer on the project. That, coupled with the fact that Crichton had recently become a hot property following the success of Jurassic Park, helped the pair successfully negotiate a series order with NBC, after the network initially only agreed to a two-hour movie.

2. GEORGE CLOONEY "BEGGED" FOR AN AUDITION.

"George Clooney begged me for a part," said executive producer John Wells. The 33-year-old was by that time a TV veteran who hadn’t yet found his breakout role (one of his earlier roles had been on a short-lived 1984 CBS sitcom titled E/R). "George was the first person to audition. He came after me for it," recalled Wells. "Our second day in the office, George showed up and wouldn't leave until I'd let him audition ... George got his hands on the material and was like a dog with a bone."

3. ERIQ LA SALLE WAS GLAD THAT HE HAD KEPT HIS COSTUME FROM A PREVIOUS ROLE.

La Salle came into his ER audition in scrubs, which he had gotten on The Human Factor, a medical show he worked on with John Mahoney two years earlier.

4. CAROL HATHAWAY WAS SUPPOSED TO DIE.

Julianna Margulies’s character was not supposed to survive her suicide attempt in the pilot. But audiences liked Margulies—and her chemistry with Clooney—so the producers opted to keep her alive, and employed.

5. AN ABANDONED, POSSIBLY HAUNTED HOSPITAL WAS USED FOR THE FIRST EPISODE.

“24 Hours” was shot at the former Linda Vista Hospital in Los Angeles's Boyle Heights neighborhood. It was built in the early 1900s as a hospital for Santa Fe Railroad employees. The movies End of Days and Outbreak also shot scenes there. The people behind the paranormal documentary/reality TV show From Beyond claim they heard voices and were “grabbed and scratched” when they spent time there. The other 330 episodes of ER were shot at a replica of Los Angeles County General Hospital’s emergency room at Warner Bros. studios in Burbank.

6. CAST AND CREW TOOK FOUR TRIPS A YEAR TO CHICAGO TO SHOOT THE EXTERIORS.

Since ER was set in Chicago, it was important that the production did some shooting in the Windy City. Sometimes scenes would be shot without the script being finished, so the actors only had a vague sense of what their characters were experiencing. The last scene of the classic “Love’s Labor Lost,” when Dr. Greene breaks down on the L, was filmed two months before the rest of the episode, so the script wasn’t written yet. All Anthony Edwards was told was that he’s going to feel like he killed a mother.

7. NOAH WYLE ONCE ACTED WITH MONO AND A 104-DEGREE FEVER.

Wyle was hallucinating before shooting “Love's Labor Lost.” The medical tech on the set gave him an IV; Wyle performed his scenes with a bag of saline in his pocket.

8. WYLE TREATED AN ACTUAL MEDIC WHO WAS DEHYDRATED.

While on location in Africa years later, the on-set medic passed out from the heat. Wyle took a functioning IV, stuck a needle in him, and revived him with a bag of saline. He credited learning how to do that “through osmosis.” Wyle played a doctor on ER more than any other actor: 254 episodes

9. THE CAST LIKED TO PULL PRANKS WITH FAKE BABIES.

Anthony Edwards would always try to figure out how to involve an alien baby in the proceedings to bring some levity to the sometimes tense set. Clooney was known to play football with a very expensive silicone baby prop.

10. THERE WAS ONLY ONE NOTICEABLE MISTAKE DURING THE LIVE EPISODE.

Performing the season four opener, “Ambush,” live was Edwards and Clooney’s idea. It was performed live twice, once for the east coast and once for the west coast. During the second performance, the actor who played the HIV-positive patient accidentally dropped his syringe before he threatened the staff with it.

11. LA SALLE ASKED PRODUCERS TO END HIS CHARACTER’S RELATIONSHIP WITH ALEX KINGSTON’S.

La Salle made producers end Dr. Benton’s romance with Dr. Corday because he was uncomfortable with what the interracial relationship was saying to African Americans. La Salle claimed he was uncomfortable that his relationships with black women on the show were dysfunctional, whereas his one relationship with a white character was not.

12. SOME ACTORS ASKED TO BE KILLED OFF.

Maura Tierney, who played Dr. Abby Lockhart from 1999 to 2009, asked to be killed off. Instead, she was given a juicy enough storyline that she was okay with sticking around until the end of the series. When Edwards told John Wells that he was leaving the show after eight seasons, Wells said that Dr. Greene was too important a character to just walk away from the show, so he asked Edwards: "'Do you mind if we kill him?' And I was like, 'Nope!' You’ve gotta do what’s best for the show, so that’s okay.” When Kellie Martin decided her character, Lucy Knight, wasn’t working for her, she requested that her departure be made “big.”

13. DAVID KRUMHOLTZ WAS FEARED AFTER HIS GUEST SPOT.

The day after “Be Still My Heart” aired on February 10, 2000, Krumholtz—whose character, Paul, fatally stabbed Lucy—"went out in Burbank, and went shopping in a mall or something," the actor recalled to the Los Angeles Times. "I got recognized at least five or six times from that episode, and people were actually frightened! I couldn't have been more unassuming to those people that probably were surprised to see that I was short and sweet and smiley." Nearly a decade later, when he was starring on Numb3rs, he was still regularly asked about that episode of ER.

14. A LOT OF HOSPITAL SCRUBS WERE USED IN THE 15 SEASONS.

The producers estimated that, over the course of the series, they had procured approximately 130,000 sets of hospital scrubs.

15. THE SHOW SAVED LIVES.

A 28-year-old woman in Texas discovered she had a brain tumor because her tongue went out to the side, just like Dr. Greene’s tongue did when his brain tumor returned. The woman’s tumor was caught early and she survived. A USC study found that subjects were 65 percent more likely to change their eating habits if they watched the episode about obesity. And a 2002 study by the Kaiser Family Foundation discovered viewers “increased their knowledge” of HPV and contraception after viewing episodes of the show.