Revealing mistakes: When Jerome's roommate, the fashion designer, is sewing on his machine, it wasn't threaded correctly. The spool was on the bobbin loader, not the spool pin where it should be.
Continuity: When Jerome visits Professor Sandiford, Sandiford is smoking a cigarette that disappears and reappears between shots.
Factual errors: When Jerome is the bartender at the party, he twists the top off of the beer and gives it to Jonah. Hoegaarden does not come in twist off bottles.