Continuity mistake: After Helen says, "Maybe a pound or two or sixty." Her hands are by her side, the shot changes one hand is now on the counter. (00:09:05)
Revealing mistake: When Brian slams down the phone the whole wall moves.
Return to Nantucket: Part 2 - S1-E4
Revealing mistake: Carol closes her eyes before Helen throws the pie in her face. There was no way she could have known it was coming because Helen was hiding the pie.