Revealing mistake: When Jim is rescued from the snow (thrown over Reggie's shoulder), he moves his leg, although he is supposed to be unconscious.
Other mistake: In the scene where Jim is getting ready to lose his virginity there is a blood spot on the top right hand side of his forehead. Afterwards he's seen up journaling and the blood has switched sides.
Continuity mistake: In the beginning of the movie where Jim is woken by a screaming woman, he first looks towards her, but in the next shot he leans on his elbows to see her better.
Continuity mistake: When Jim attempts to escape Reggie's apartment while having the withdrawals, from the close-up shot it is clear his legs are inside the room, but when Reggie tries to pick him up, Jim is now sitting across the doorway.
Continuity mistake: When Pedro goes to the lockers room to steal something from the rival basketball team, we see that he manages to unlock one padlock, but in the next shot the padlock makes a loud noise as it unlocks.