Trivia

All of Hesher's "persona", according to Joseph Gordon-Levitt, is inspired by late bass player from Metallica, Cliff Burton. Not only that, but the movie features a significant amount of music from the "Burton" era, including the solo that Hesher plays in the garage (Anesthesia, from the Kill 'Em All album) and, of course, the Hesher lettering.

In the scene where Hesher criticizes T.J. for not taking walks with his grandmother, the man who he refers to that rapes old women was actually serial killer Albert DeSalvo, more commonly known as the "Boston Strangler."

Natalie Portman wore two pairs of underwear at the same time for her role.

The skull tattoo on Heshers arm resembles a same like tattoo from late Metallica's bass player Cliff Burtons' arm and it is based on the logo from the 80ies horror punk band The Misfits.

Elephants make several appearances in the film. Rainn Wilson's character is watching a TV show about elephants and we hear them in the background, the car dealership has a large pink elephant on the roof and beside TJ's bed there is a figurine of another elephant.