Revealing mistake: As Fester looks at the mirror, it shatters. After he asks a question, it falls off the wall. After it does, you can see what appears to be someone's fingers pushing from the other side to knock the mirror down. That spot on the wall is obviously fabric covering a hole.
The Addams Family (1964)
1 revealing mistake in Cousin Itt's Problem
Starring: John Astin, Carolyn Jones, Jackie Coogan, Ted Cassidy
The Addams Family Goes to School - S1-E1
Continuity mistake: After Mr. Hilliard goes through gate and nears the house, it's really at the real house. A second later, he's approaching the now-familiar front porch on the studio set. This is easy to tell because the layout of the two porches are radically different.
Grandmama Addams: Fester, You're not cheating.
Uncle Fester: Sorry.
Trivia: Originally, Lurch was supposed to remain mute for the entire show. In the pilot, when the bell is first rung to summon Lurch, Ted Cassidy ad-libbed the line, "You rang?" This caused everybody to burst into laughter and from then on Lurch would talk.
Question: How was effect of the light bulb that lit up whenever Fester put it in his mouth achieved?
Answer: Basically from what I understand, they stuck the innards of a small flashlight into the base of the bulb and put a little switch on it. When he put it in his mouth and bit down, his teeth would hit the switch, which would turn on the flashlight and made the bulb light up.
TedStixon