Jason Segel read for the part of Evan, but by the time the movie was made, he was too old for the part.
Seth Rogen wrote the part of Seth for himself, but got to old to play the part. The role went to Jonah Hill and Seth Rogen instead played Officer Micheals.
The lead characters, Seth and Evan, are named for writers Seth Rogen and Evan Goldberg.
Writers Seth Rogen and Evan Goldberg went to party at a house owned by a midget and a bodybuilder while writing the movie.
Writers Seth Rogen and Evan Goldberg started this script when they were just 13 years old citing the reason as being "we just wanted to see if we could write a movie."
Seth Rogen's father Mark Rogen appears as the baseball bat wielding dad when Seth and Evan are fleeing the police through backyards.
The word "fuck" is used 186 times in the movie. The movie itself is only 118 minutes long. That averages to approx. 1.6 uses of the word per minute. Around 84 are said by Seth.