In the TV world, 1999 was a pretty important time. The multi-Emmy Award-winning drama series “The Sopranos” and “The West Wing” premiered that year, as did Nickelodeon’s beloved “SpongeBob SquarePants,” which has spawned two movies and even a Broadway musical, and Seth MacFarlane’s raucous Fox animated “The Family Guy.”

But one of the most fondly remembered series — which kicked off the careers of actors including James Franco, Seth Rogen, Jason Segel, Linda Cardellini, Busy Philipps and John Francis Daley — didn’t even air its complete season. NBC’s high school dramedy “Freaks and Geeks” premiered Sept. 25, 1999, created by a pre-“Bridesmaids” Paul Feig and executive produced by Judd Apatow. The producing talent also included “School of Rock” writer Mike White and “Bad Teacher” director Jake Kasdan, and the show also featured guest stars including Ben Foster, Rashida Jones and a baby-faced Shia LaBeouf. But after only averaging 6.8 million total live viewers for the season, it barely cracked Nielsen’s Top 100 rankings, and the broadcaster opted not to air the final three episode of its 18-episode season.

“When we came out, it was so exciting to get all that critical response,” says Feig. “But when you get the critical response and you’re still getting terrible ratings, it’s such a bitter pill to swallow. We got the show picked up and you want to celebrate, and they go and say [your time slot] is Saturday at 8 p.m. You’re like, ‘Oh my god, there’s no way we’re going to survive that time slot’ — especially back then it was just VCRs. No one had TiVo. Anybody who wanted to watch the show was out having fun, not at home watching a high school show.”

Still, the show did manage to find a devoted audience, and over time it even got to release those final episodes (on then-network Fox Family, which is now Freeform). The accessibility of home entertainment with DVD releases allowed the show to pick up additional, albeit late, fans. Between the themes of adolescence that the show explored and the talent it employed bringing the stories to life, it became something of a modern cult classic that Paley Center for Media TV historian Ron Simon says defied the conventions of the teen genre.

“It really wants to look at the painful realism of growing up,” he says. “That was difficult for the networks to deal with. They wanted to do a more idealized version of high school. They didn’t want as much pain and confusion. Certainly ‘Freaks and Geeks’ brought that.”

But its intimate realism, Simon adds, is why the series’ fans cherish the show. “Anyone who watches it immediately flashes back to their own high school days. You recognize the hierarchies, just where you belong and how difficult it is almost every day to negotiate so many landmines of high school. I think you felt that in the show.”

Set at the fictional William McKinley High School outside of Detroit-during the 1980-81 school year, “Freaks and Geeks” revolves around the brilliant “mathlete” Lindsay Weir (Cardellini) who rebels and starts hanging out with the school’s outcasts and slackers, Daniel (Franco), Ken (Rogen), Nick (Segel) and Kim (Philipps) — much to the concern of her worried parents (Joe Flaherty and Becky Ann Baker). The geeks are represented by Lindsay’s freshman brother Sam (Daley) who navigates the often-mean hallways of McKinley High with his equally nerdy pals Neal (Samm Levine) and Bill (Martin Starr).

“I always wanted this show to be that mix of really real behavioral comedy,” but also to carry dramatic weight, explains Feig. “It had a reality to it, because that’s what I hadn’t been seeing on television. The show was like my antidote to all the high school stuff that drove me crazy that I used to see on TV. It was all soap opera.“

At the time, it was more common for teenagers to be portrayed having very adult problems with “sex and relationships,” Feig recalls. But that didn’t reflect his experience. “I couldn’t even get a date. The thought of asking a girl out or making out with somebody — God forbid the thought of having sex with anybody — was more than my brain could take.“

Feig, who created Sam from his own experiences, was an old friend of Apatow’s through the standup comedy scene. Apatow cast him in the 1994 movie “Heavyweights,” which Apatow executive produced and co-wrote, and when Feig made an “out-of-pocket feature film thant I spent $30,000 of my money on” in 1997, Apatow came to the premiere and “really liked” the project, Feig recalls. It was right after Apatow made a deal at DreamWorks, and Apatow told Feig to contact him if he ever came up with an idea for a TV series. Feig did after he wrote the “Freaks and Geeks” pilot.

“It was kind of life-changing,” says Feig about the series. “I was a struggling actor at that point. I was a regular on ‘Sabrina, the Teenage Witch,’ but I had been written out of the series after it became successful. So I had no job. I had spent all my money on this independent film. I was really in dire straits. Suddenly I had a career as a writer and showrunner.”

Apatow connected to the material of “Freaks and Geeks” because he felt like both a nerd and a burnout in high school. “I switched groups a couple of times during those years,” he says.

And while Feig imbued his personality into Sam, Apatow says the stories about divorce and problems at home were inspired by experiences he had. “Bill’s mom dating the gym teacher and Neil getting obsessed with ventriloquism as a way of dealing with his parents’ divorce, those were episodes I was interested in because that defined a lot of my high school experience,” he explains.

As a writer and director, notes Apatow, he was also inspired by what Feig was trying to create with the series. “I had just finished working on the last season of ‘The Larry Sanders Show’ and for myself personally, I tried to pretend I was still working for Garry [Shandling], but except it was about high school. In my mind I said, ‘I think the best way to write this is with all the rules of the Larry Sanders Show’ — about truth and heart.”

For Apatow, Shandling “was always a voice in my head about talking about the struggle to be a human being and to want to love, to survive hardships and heartache. It was very helpful for me to have come out of the Garry Shandling school right at the moment we started ‘Freaks and Geeks.”’

Emmy Award-winning casting director Allison Jones was brought in to find the kids to embody these complex themes, and Feig notes she understood what they were trying to accomplish right away. “She was bringing in tons of kids, but all really interesting, different kids,” says Feig. “We did tons of casting sessions. It was very apparent each time the right person would walk in. Some of them weren’t exactly the way they were written in the script. We decided let’s just rewrite the character.”

Segel’s Nick was one character who changed, originally written to be “more of a gearhead car guy — I think he was even described as a fireplug,” says Feig. But when Segel, “this big, tall, handsome guy with this intersting delivery and strange personality” walked in, things changed. Feig admits he was apprehensive about Segel at first because it wasn’t what he envisioned for the character, but Apatow convinced him to rewrite because of how good Segel was in the audition. At the end of the day, Feig admits it was the right move: “Letting Jason Segel walk away would have been a crime.“

Ditto Rogen. “He had such a unique voice and personality,” remembers Feig. “He was hilarious and he kind of had this really sarcastic delivery. We were just completely blown away by him. It was such a nice discovery.”

The character of Sam was harder, though. “We’re trying to cast a kid who reminded me of myself,” Feig says. “He was supposed to be really tall because I was really tall in school. But all my bullies were little short guys. They had picked on me because I couldn’t fight back.”

The then-14-year-old Daley, who Feig notes looked like he was closer to 10-years-old, sent in a casting tape. Feig admits he didn’t want to cast him at first because he looked so young. But then “he started reading,” recalls Feig. “I was like, ‘Oh God, that’s exactly what we were. Some of us in school were so mature that they looked like they were early 20s and then some of us — we were babies, completely underdeveloped, emotionally, mentally and maturity-wise, not very developed.”

Daley feels he aced the audition because he so identified with Sam. “I always felt kind of fringe and not really fitting in with that kind of archetype for a kid actor,” he says. “Then I got the ‘Freaks and Geeks’ audition. I couldn’t pass it up. I had to go in because I felt it spoke to me on a personal level, and I’m glad I did.”

“Freaks and Geeks” was the first pilot he had ever done. “It gave me a crash course in learning the things that I always dreamed of doing, but never thought actually possible or probable,” says Daley. “Here are these other young people sharing that experience with me. The fact that Judd and Paul, I think, were my age or younger than my age now is incredible to me. It was just like, in many ways, the beginning of what launched them into super success.”

Much like in the series itself, Daley bonded with his fellow geeks. “I spent most of the time with the kids that were closest to my age,” he says. “I had my dad on the set. He was my guardian. After the fact, when we were all came into our 20s and 30s, that separation fades away and you get to spend time with people as peers.”

Like Franco, Rogen and Segel, Daley is also a writer and director, penning “Horrible Bosses” with his partner Jonathan Goldstein, as well as “Spider-Man Homecoming” and directing films such as 2015’s “Vacation” and 2017’s “Game Night.” Bringing it full circle, Daley and Goldstein are on tap to direct “Dungeons and Dragons,” which Sam and his friends play in the final episode of “Freaks and Geeks.”

Many of the cast and the filmmakers have continued to work together over the years. In fact, Rogen appears in Franco’s latest film as a director, “Zeroville,” which opened on Sept. 20.

“I think we are all proud of each other for what we’ve accomplished,” says Apatow. “And more importantly, the adults everybody has become. Everybody is really nice and smart and compassionate. That’s what’s most rewarding about the experience.”

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