All There In The 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.
The Cast Show Off: Jon Heder, an animation school dropout, did all of Napoleon's hideous drawings himself. He also choreographed Napoleon's big dance.
Completely Different Title: Bus Man in Japan, though it was reverted recently to the original English name, after too much controversy since it's original release in Japan, since that name is a wordplay from the movie Densha Otoko (Train Man)
Dawson Casting: Most of the main cast of high school students were in their 20's 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.
No Budget: It only took $400,000 to produce Napoleon Dynamite and nearly half of that was spent for the post-credits scene.
Throw It In: Napoleon's dancing was entirely improvised by Heder.
Also, 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 is what is seen in the film. It turns to be actually funnier.
Unintentional Period Piece: Subverted, in a way. The film immediately dates itself at the start by setting the year as 2004-2005, but the film's aesthetic more resembles the 80s, with only one song from the 2000s at the end. When asked what time period the film takes place in, Jared Hess replied "Idaho." Most assumed that this was a case of Teasing Creator, but it was his way of explaining just how behind the times the state is. Many who visited Idaho after the film came out were quick to note how little the creators exaggerated its distance from the pulse of the rest of society.
Write What You Know: Jared and Jerusha Hess are from a small Mormon community in Idaho, and Pedro was based on Jared's friend.
Many of the events are also from the directors' own life, such as the cow shooting scene, the "Happy Hands" club, the "I like your sleeves" line...
The TV series:
Role Reprisal: Practically the entire cast of the movie voices their respective roles in the show.