Jon Heder drew all of the drawings in the movie except the unicorn.
Having the food plates spell out names in the opening credits was actor Aaron Ruell (Kip)'s idea. The rest of the sequence was designed and executed by Pablo Ferro.
The Cast Show Off: Jon Heder both inverted and played this trope straight: He inverted it as he, an animation school dropout, did all of Napoleon's hideous drawings himself, but played it straight by choreographing Napoleon's big dance.
Dawson Casting: Most of the main cast of high school students were in their 20s or 30s, with the exception of Tina Majorino and Haylie Duff who were both about 18. Averted with the extras, played by actual high school students.
Follow the Leader: After the success of the film, many TV commercials (notably candy commercials for Skittles and Trolli) tried to emulate the film's style by featuring absurd, deadpan humor and realistic-looking kids in late '70s - early '80s clothes.
No Budget: It only took $400,000 to produce and nearly half of that was spent for the post-credits scene; and a fourth of that went into getting the rights to "Canned Heat"
The Red Stapler: You've definitely seen at least one person with the Vote for Pedro shirt by now. It's also easy to sell as a knock-off piece of merch since it's not a difficult thing to make. And yes, you can also buy your very own Rex Kwan Do ensemble, too.
Napoleon's dancing was entirely improvised by Heder... to three different songs. It was cut together from 10 minutes of dancing footage, and they weren't even done shooting since the film ran out in the process.
The scene where Kip is giving the demonstration with the van and the dinnerware. Originally, he was to roll over it, and the plastic would deform but reshape itself, to which Kip was to say, "Pretty cool." However, the plastic was unable to comply due to the laws of physics, and that's what made it into the film.
When we first meet Kip, he's sitting at the computer mumbling a love poem, the words to which weren't in the script - they were said on the spot by actor Aaron Ruell.
Word of God: According to the DVD Commentary, the woman riding her bike to Uncle Rico's van at the end is supposed to be his ex (the credits identify her only as "Woman on Bike"), and their break-up is the biggest reason why he seems so unhinged.
Write What You Know: Jared and Jerusha Hess are from a small Mormon community in Idaho, and many of the events are from their own life, such as the cow shooting scene, the "Happy Hands" club, the brothers slapping each other, the "I like your sleeves" line...
Executive Meddling: The entire reason the series exists. It was created solely as filler for when Family Guy was in its off-season. Not surprisingly, the ratings weren't good enough to justify a second season.
Role Reprise: Practically the entire cast of the movie voices their respective roles in the show, except for Trevor Snarr, who originally played Don, and Carmen Brady, who played Starla. Both are instead voiced by producer Jared Hess. Yes, that means he plays a woman in the show.
Screwed by the Network: Fox pretty much had no faith in the show, as they frequently put the show in time slots where it was usually preempted by football games, which quickly resulted in low ratings and the series was cancelled by the network after just six episodes.