If you think about it, coming up with a successful medical drama can be tricky for a show creator. That’s because there are several elements that need attention all at once. First, you need to have a convincing plotline. Your medical cases should also be compelling, and realistic. If you can make this happen, chances are your medical drama would be successful, just like “ER”

Indeed, “ER” went on to become one of the most Emmy-nominated tv shows in history. The show also saw the rise to fame of Hollywood superstar George Clooney. Meanwhile, its cast also included Julianna Margulies who went on to star in the CBS legal drama “The Good Wife.”

It’s been years since “ER” went off air. Yet, it remains a celebrated show. Because of this, we thought it would be fun to reveal 15 things you never knew about this incredible medical drama:

15 The Script Was Already 20 Years Old By The Time The Pilot Was Made

A behind the scenes look on the set of ER via twitter.com

While speaking with Entertainment Weekly, Warren Littlefield, the former president of NBC Entertainment, recalled, “[Creator] Michael Crichton’s pilot script for ER was 20 years old and approximately 150 pages. It came out of his experience as a med student in Boston. It was all over the place, more chaos than order.”

14 Noah Wyle Landed His Part After Pretending To Draw Blood From The Casting Director With A Pencil

A scene from ER via glamour.com

While speaking with The Hollywood Reporter, casting director John Levey recalled, “Noah tied off my bicep with some kind of a wrap, and then, using a pencil, he pretended to draw blood from me. Crichton was laughing his head off. It was a brave and exciting audition, and the rest is history.”

13 There Was Trouble Casting Eriq La Salle Initially, Because They Couldn’t Poach Actors From Other Warner Bros. Shows

Eriq La Salle in a scene on ER via glamour.com

Warner Bros. head casting director, Barbara Miller, didn’t allow her casting directors to poach from each other’s show. And it just so happens that La Salle was starring on a different medical show around this time. Fortunately, she eventually relented and just in time, too. As Levey revealed, “He was the last person cast.”

Related: 20 Most Beautiful Women George Clooney Was Linked To (Before Amal Alamuddin)

12 Warner Bros. TV Originally Wanted George Clooney For A Cop Show, But ER Snagged Him In The End

George Clooney on the set of ER via twitter.com

Executive producer John Wells told The New York Times, “Les [Moonves, now the CBS chief executive, then the head of Warner Brothers studio] had made a cast contingent deal for a crime show with George, but George showed up in my office and said he’d heard about our show, and he liked the part better than the legal show.”

11 In An Early Version Of The Script, Julianna Margulies’ Character Died

A scene from ER via pinterest.com

Margulies' character, Carol Hathaway, originally ends up killing herself. However, after screening this, Kevin Reilly, former NBC VP of drama development, revealed, “One thing that came out of the research was how sorry everybody was to see Julianna go. So we just looped a line in saying, ‘It looks like she’s going to make it out of the coma!’”

10 After Screening The Original Pilot, Execs Thought They’d Never Get It On The Air

A behind the scenes look on the set of ER via weheartit.com

The pilot didn’t please Don Ohlmeyer, the former NBC West Coast president. Wells even recalled, “We waited about an hour after the screening for them to come and give us notes. Finally, Warren came into the room and said, ‘There is really no point in giving the notes because Don is never going to put it on the air.’”

9 The Show Was Engaged In A Nasty Feud With Chicago Hope, Even Attracting The Ire Of Mandy Patinkin

A behind the scenes look on the set of ER via imdb.com

Preston Beckham, NBC’s former head of scheduling, explained, “I had a feeling CBS would move Hope to Monday night at 10 the day after New Year’s. So we announced we’d repeat the ER pilot on that day. In early December, Don got a call from Hope star Mandy Patinkin, who wanted to know what NBC had against his show.”

Related: Here’s How These 15 Grey’s Anatomy Moments SHOULD Have Happened

8 Abraham Benrubi Bet George Clooney $5 That The Show Would Be #1 By The Time It Reached Its Fifth Episode (He Won)

Abraham Benrubi on ER via pinterest.com

On the show, Benrubi played Jerry Markovic and he revealed, “I said to George it was going to be the No. 1 show in television by the fifth episode. He said no way. We wound up betting on it. It was No. 1 after the fourth episode and George still owes me that $5.”

7 There Were Times When The Show Would Shoot Scenes Without Editing

A behind the scenes look on the set of ER via vox.com

Producer Chris Chulack explained, “Sometimes we would shoot a five-page scene without an edit. The actor that had the last line was under huge pressure because if he broke we’d have to go back to the beginning.” He also revealed, “We took seriously the idea that we were also an action show.”

6 When Kellie Martin First Joined The Show, Noah Wyle Didn’t Really Treat Her Well

Kellie Martin in a scene for ER via twitter.com

Wyle revealed, “I was not nice all the time to Kellie. Kellie came on that show and we were like rock stars.” He added, “We worked extremely hard to be the No. 1 show over those five seasons, and when Kellie came on, or whenever anybody came on, it was like, ‘Earn your keep!’”