Other mistake: When Peter is dancing to his musical number on top of the table, his head continually shrinks until the end of the shot, where his head is around a third of what it was originally.
Fifteen Minutes of Shame - S2-E12
Other mistake: Right at the end, when Peter takes out the Bible, the front cover is on the wrong side, i.e the back.
Other mistake: In the scene where Einstein is stealing Smith's theory, when Einstein pulls the metal bars down, they should land on Smith's head, but Smith inexplicably moves forward and the bars land on his back.
Other mistake: After Brian says Chris is tweaked and Chris says maybe the toad is Meg's, the bubbles in the aquarium stop moving.
Other mistake: In the flashback to Brian and Peter playing checkers, Brian's piece is not on the back row when he says "king me."
Other mistake: Throughout many episodes, it's discovered that anybody that touches Death immediately dies. When Stewie learns that Death has come for Peter, he immediately touches his finger to lead him inside but manages to live.
A Picture Is Worth 1,000 Bucks - S2-E11
Other mistake: Brian says he met Antonio Monatti when he was with Andy Warhol in the '70s. This is an impossibility. Only several episodes earlier (in episode Brian in Love), we find out that Brian is 7 years old.
