Continuity mistake: After Stevie becomes catatonic, a wrapper from a chocolate bar lands on his face, covering his glasses. The shot cuts and it's on his shoulder and then cuts again and it's on his face again.
Continuity mistake: When Malcolm is throwing the dodgeballs at Stevie, the number of balls in the bag changes between shots.
Character mistake: When Otto tells Francis he has to put a horse down, Francis objects saying he's never killed anything bigger than a poodle, and that was an accident. However, in season 4 (episode 11), Francis accidentally killed Otto's pet cow. (00:11:30)
Answer: Francis is only allowed to talk on the phone at school for three minutes a day. I think the code gives him free access to talk to his girlfriend.