Continuity mistake: When we first see the padded envelope, Josh has put three stamps on it, spaced out. Then when he finally retrieves it, there are 8 stamps. Admittedly his friend might have replaced them with the correct postage, unlikely though it is, but unforgivably, the address is completely different - most noticeable is the middle line. The first time it's "5893 Tyler", and the second time it's "695 University Dr." The sender's address also changes from "Columbus St." to "549 Campus Drive".
Continuity mistake: When Tom Green is playing the guitar (after the mouse has been dropped in and the snake's head is somewhat near it) the hand with which he plays the guitar switches several times as the view of his face switches. When it's a profile view, he strums on the neck of the guitar with his left hand. When it's a straight view, he plays the bottom of the guitar with his right hand.
Continuity mistake: In the scene where Josh is having the dream that Tiffany is watching the tape with her friends, when the camera zooms in on Tiffany as the movie is playing, look behind her head in the mirror and you will see the movie scene where Beth walks towards Josh in her underwear. It then goes to the television, where it plays the same scene again, then continues.
Continuity mistake: Not only does Josh only put three stamps on the letter and at the end and in the dream sequence it has eight, but in fact in the same scene (at the beginning where he actually puts the stamps on), the number of stamps changes from three to eight with only a few seconds in between.
Continuity mistake: In the scene where the "fat" girl is sitting on the swing flirting with the geeky guy, she smiles and has perfect, straight teeth, in no need of braces. Later, in the scene where the geeky guy is introducing the fat girl to his dad at the door, the fat girl smiles and has braces on.
Continuity mistake: There is a snake in a glass cage in the dormitory room. Several times in the same scene the snake completely changes positions in the cage.
Continuity mistake: In the scene where the car blows up after jumping the bridge they walk away from the car and are lined up just before it explodes and after it explodes E.L. turns slightly then realises that he's not supposed to yet he quickly turns back. This is before they all turn around in unison.