Once it became clear that Freaks and Geeks was going to leave behind a beautiful corpse, executive producer Judd Apatow decided to take another stab at network television and create Undeclared. The show, which premiered on September 25, 2001, revolved around a group of freshmen at the fictional University of Northeastern California, particularly the trials and tribulations of the geeky and too-nice-for-his-own-good Steven Karp (then-newcomer Jay Baruchel).

While Steven deals with his recently separated and lonely dad Hal (Loudon Wainwright III), he also has to work around his feelings for his neighbor Lizzie (Carla Gallo), the fellow freshman to whom he lost his virginity, and navigate his friendships with his roommates, including Ron Garner (Seth Rogen) and Lloyd Haythe (Charlie Hunnam). An impressive roster of future stars appeared on the series, including Amy Poehler as head RA Hillary, Jason Segel as Lizzie's jealous ex-boyfriend Eric, and Kevin Hart as the religious Luke. To celebrate the series' 15th anniversary, here are 15 major facts about Undeclared.

1. THE IDEA STEMMED FROM JUDD APATOW'S DESIRE TO KEEP THE FREAKS AND GEEKS CAST AND CREW EMPLOYED.

"I enjoyed my writing staff and production staff so much that I just wanted to try and keep everyone working," Apatow admitted of Undeclared's origins. "So we thought, what would be the best show we could come up with that allows us to hire a lot of these same people and a lot of these same actors? And we thought, well, by the time we get this on, most of these Freaks and Geeks kids will be college age; let’s do a college show! It was as lazy as that."

2. APATOW CAST THE ACTORS BEFORE WRITING THE PILOT.

Fox ordered six episodes before ever seeing a script, giving Apatow the chance to talk to the actors about what they were like as college freshmen. He then wrote the characters based on what they said. Improvisation and messing around with the dialogue was also encouraged.

3. JASON SEGEL WAS THE ORIGINAL CHOICE TO PLAY STEVEN KARP.

But Fox didn't believe Segel was enough of an underdog. Instead, Apatow cast the Freaks and Geeks star in the recurring role of Eric, Lizzie's obsessive ex-boyfriend.

4. JAY BARUCHEL BEAT OUT A REALITY TV STAR TO WIN THE LEAD.

Colin Mortensen from Real World: Hawaii tried out for Steven. "Thank God you beat that guy," Rogen told Baruchel at the 2011 PaleyFest reunion.

5. LOUDON WAINWRIGHT III DID NOT WANT TO AUDITION.

The musician/actor hated auditioning, and because auditioning in front of network executives was particularly stressful, Apatow simply told Fox he was out of town. Instead, Apatow showed the network a tape of Wainwright. "So I saved him the trouble, even though he was really only five minutes away at the time," Apatow admitted.

6. IN A WAY, IT HELPED LAUNCH DANNY MCBRIDE'S CAREER.

Timm Sharp, who played Steven's suitemate Marshall Nesbitt, had to drop out of David Gordon Green's All the Real Girls (2003), where he was set to play "Bust-Ass." Danny McBride ended up making his big-screen debut in the part instead.

7. TOM WELLING AUDITIONED, BUT APATOW THOUGHT HE WAS TOO GOOD LOOKING.

“I had this kid, Tom Welling, come in for Undeclared, and he was great, but too good-looking," Apatow told The New York Times in 2007. "We put him in a small part in the first episode as a frat brother. I’d tell people, 'There goes the next Tom Cruise.' Six weeks later he was cast as Superman in Smallville."

8. APATOW HAD A "NO NAPSTER JOKES" POLICY.

"I'm trying to make the show somewhat timeless," Apatow said in October 2001, when the series was just a few episodes old. "I don't want to do 800 Napster jokes, and then Napster goes under, and someday in reruns, my show looks ridiculous. I just try to keep it in that netherworld where the show hopefully makes as much sense in 10 years as it does now."

9. AN ENTIRE STORY INVOLVING TED NUGENT WAS TAKEN OUT AND REPLACED IN THE SECOND EPISODE.

In "Oh, So You Have a Boyfriend", the A-story had Steven and Lizzie attending an on-campus screening of American Pie (1999). In the originally shot but ultimately unaired version, in an episode then titled "Full Bluntal Nugety," Steven and Lizzie's first date involved them going to a Ted Nugent lecture, where Uncle Ted himself cameoed. Fox thought the Ted Nugent thing was possibly "too obscure."

10. KEVIN RANKIN REMEMBERED AMY POEHLER BEING INSECURE.

Kevin Rankin, who played RA Lucien, compared Amy Poehler—who officially joined SNL a few weeks into Undeclared's run—to a Beatle in 2010. "She's like John Lennon-esque in her genius of comedy," he said. "She was so insecure and we would do a take and she'd be like, 'That's just not funny.' I'm like, 'No, you're doing great,' not knowing who she really was at the time."

11. MENTIONING TOPHER GRACE STARTED A FEUD.

Mark Brazill, co-creator of That 70s Show, was upset that he heard from another party that Apatow wanted to get his show's star, Topher Grace, to guest star on Undeclared. In a heated email exchange that was leaked to the public, Brazill accused Apatow of stealing an idea he was going to use for a new TV series for a sketch on The Ben Stiller Show.

12. FOX WANTED A LAUGH TRACK.

Baruchel remembered that throughout the production of the series, as far as the cast and crew were concerned, there was a "sword hanging over our heads"—the constant threat of cancellation. "They thought we needed a laugh track because otherwise, how will the audience know where the jokes are?" Baruchel added. "Stuff like that. We’d get notes like 'We want it to be more like Road Trip,' whatever that means."

13. APATOW DIDN'T TAKE THE IMPENDING CANCELLATION WELL.

Apatow framed a rave review from TIME magazine of Undeclared and sent it to the Fox executive who was about to cancel the series after 17 episodes. It came with a note that used rather adult language.

14. BOTH SUPERBAD AND ADVENTURELAND GOT THEIR STARTS ON THE SET OF UNDECLARED.

Seth Rogen got his start writing for television on Undeclared. He showed Apatow a script he and his friend Evan Goldberg had written called Superbad. Apatow ran a table read of the script with Rogen and Segal as the leads, David Krumholtz and Kyle Gass—both of whom played Rogen's buddies on the show—as the cops, and as future Superbad director Greg Mottola later recalled, the rest of the Undeclared cast reading the other parts. Mottola, who directed five episodes of Undeclared, immediately asked Apatow to think of him if the movie ever got made.

Mottola himself later wrote and directed Adventureland (2009), with the help of an inebriated evening with Undeclared's writers. "One night I was getting drunk with the writers from Undeclared and we were swapping worst-job-ever stories, and I talked about the summer of 1985, when I worked at an amusement park on Long Island, the kind of place where someone would pull a knife on you if they wanted a better prize than you were giving them," Mottola explained. "And at one point one of my friends, a writer on the show, Jenny Konner, said, 'You should write about that.' I’d already started outlining the young-love story, and I thought, 'Well, that kind of fits.'"

15. A FORGETTING SARAH MARSHALL DVD EXTRA REVEALED THE FATES OF STEVEN, LIZZIE, AND ERIC.

According to Segel, nothing came of Steven and Lizzie's relationship; Eric and Lizzie ended up having a one-night stand years later, and Eric still wasn't over her. When Carla Gallo was asked what her character would be up to now, she speculated that Lizzie would probably be single. "I think she’s out there annoying everyone, being too perky," Gallo said. "Maybe still living with Rachel. They’re still single ladies on the town trying to lock down a man."