The Equation - S1-E8
Revealing mistake: The shots of Peter and Walter entering St. Claire's are recycled shots from the pilot. You can tell because their clothes change.
Night of Desirable Objects - S2-E2
Revealing mistake: When the typewriter is being used at the end, the keys being pressed don't correspond to the words appearing on the paper. Obvious from the start - the first letter pressed is on the middle row of the keyboard, but the first word typed is "unacceptable".
