1. Seth Rogen as Ben Stone
Fun fact: The Dirty Man Competition came from the real-life friendship between Rogen and executive producer Adam Goldberg. They shared it with Apatow, who included it in the movie in order "to make this group more interesting."
2. Katherine Heigl as Alison Scott
3. Paul Rudd as Pete
Fun fact: Rudd hasn't aged a day since 2007.
4. Leslie Mann as Debbie
Fun fact: Mann told Collider that she initially "didn’t want to put [daughters Iris and Maude] in the movie," but her husband, Knocked Up director Judd Apatow, finally convinced her.
5. Jason Segel as Jason
Fun fact: If it seemed like Segel, Martin Starr, and Seth Rogen ~vibed~ well in Knocked Up, it might be because they had all appeared together in Freaks and Geeks.
6. Jonah Hill as Jonah
Not-so-fun fact: Hill said that it was so hot while filming part of Knocked Up that he, Seth Rogen, and Jason Segel required oxygen on set.
7. Kristen Wiig as Jill
Fun fact: Wiig's short but show-stealing performance in Knocked Up led director Judd Apatow to "[ask] her if she had any plans to write a script for herself." She did, and that script became the 2011 blockbuster Bridesmaids.
8. Bill Hader as Brent
Fun fact: Hader, who plays a video editor at E! in Knocked Up, actually used to be a video editor at E! Whoa!
9. Dr. Ken Jeong as Dr. Kuni
Fun fact: Before becoming an actor, Dr. Jeong would practice medicine during the day and perform stand-up at night. His favorite compliment from patients was "I could never imagine a guy like you could do comedy," he told the Washington Post.
10. Maude Apatow as Sadie
Fun fact: Maude is currently studying radio, TV, and film at Northwestern University.
11. Iris Apatow as Charlotte
Fun fact: Iris, who was only 4 years old (!!!) when the movie came out, has recently garnered much attention for her role as Arya Hopkins in the Netflix rom-com series Love. (Iris and Maude are the daughters of Judd Apatow, who directed Knocked Up, and Leslie Mann, who plays their on-screen mother Debbie.)
12. Jay Baruchel as Jay
Not-so-fun fact: Jay, who's deathly afraid of roller coasters IRL, had a panic attack while filming the roller coaster scene. Director Judd Apatow apparently had to manipulate him into doing it.
13. Martin Starr as Martin
Fun fact: Starr nearly quit acting in the mid-2000s, but after the success of Knocked Up, "I couldn't really go back in time," he told the Los Angeles Times. "Anonymity is something you don't appreciate until it's gone. I'm a private person. I don't like to be gawked at."
14. Charlyne Yi as Jodi
Fun fact: Despite playing the ultimate stoner chick in Knocked Up, Charlyne said in 2007 that she had never ever been high.
15. Joanna Kerns as Mrs. Scott
Fun fact: Debra Winger, Kim Basinger, and Frances Fisher were reportedly first offered the role of Mrs. Scott.
16. Alan Tudyk as Jack
Fun fact: Tudyk was the voice of Duke Weaselton in the 2016 Disney movie Zootopia.
Harold Ramis, who played Harris Stone, died in 2014.