When Ashton Kutcher first read the script for the film, he almost turned down the role because he found it to be "very stupid." However, when he read the "you got a tattoo" scene, he could not stop laughing and agreed to take on the part.
There are Chinese characters on the sign for the Chinese drive-through restaurant where the woman on the speaker always says, "And then?" The characters, read "hai you ne" in Mandarin, can be translated, "Is there anything else?" Or, as she says, "And then?"
When Jesse and Chester are at the geek cult compound, everyone is wearing the same style of black Vans sneakers. This is a reference to the Heaven's Gate cult who all wore the same style purple Nike's.
Director Danny Leiner has made comments that, despite Leiner's urging, Fabio refused to have a goose hit him in the face as he drove off at the end of his scene (which would have been a reference to an incident where a goose hit Fabio in the face while on a roller-coaster).
In the original script, the leader of the "hot alien chicks" was supposed to say "blowjobs" instead of "pleasure" when they first confront Jesse and Chester. It was later filmed as "oral pleasure," but was ultimately changed to just "pleasure" to maintain their PG-13 rating. (The footage of the "oral" dialogue is included on the DVD.)
When Pierre asks the stoners "What is the average running speed...of a full-grown male African ostrich?", he is using a variation of Monty Python's famous "What is the air speed velocity of an unladen swallow" skit from "Monty Python and the Holy Grail" (1975).
The Nordic Alien Dudes #1 and #2 are very similar to Rolf, Egon and Arnold: Soldiers #1, #2 and #3; on the movie Mannequin: On the Move (1991), a movie on which Kristy Swanson also appeared. There is a mannequin in this movie.