Revealing mistake: Right after the "Ghost Whisperer" cutaway, while Peter, Chris, and Lois are sitting on the couch, Chris' eyes disappear for a single frame. (00:09:10)
Revealing mistake: As Stewie is walking toward Herbert's house, he just suddenly appears mid-screen.
Barely Legal - S5-E8
Revealing mistake: Every time Cleveland's tub slides out of the house, there's never any plumbing attached to it. It just sits on top of the floor so it slides out easily. In this episode its very easy to see. (00:02:50)
Boys Do Cry - S5-E15
Revealing mistake: When Lois places Stewie on the floor whilst at the Little Miss Texas pageant, one of the girls is seen looking at herself in a mirror, only she doesn't seem to have a reflection. (00:15:35)
Boys Do Cry - S5-E15
Revealing mistake: When Peter brands the cow, no burn mark is left on the cow. (00:18:20)