Halloween - Addams Style - S2-E7
Continuity mistake: As Gomez and Fester bob for apples, the apples in Gomez's bucket alternate between swirling around and being still between close up and distance shots.
Morticia, the Sculptress - S2-E9
Continuity mistake: As Morticia tries to sculpt Lurch, the boulder she is working on gets a sudden vertical crack in it from the wide shot to the close up.
Continuity mistake: After talking to Cousin It, Morticia is reading a book titled "The Law of Bigamy." As the camera does a close up on the book, the label on the spine says "Homer's Iliad".
Christmas with the Addams Family - S2-E15
Continuity mistake: When the second Santa (Grandma) knocks at the children's door, in one brief shot Wednesday already has 2 dolls in her arms.
Happy Birthday, Grandma Frump - S2-E22
Continuity mistake: As Morticia and Gomez play with the train, there is only one train on the set. When Gomez blows it up at the bridge, there is a second train in the midst of it. This is a reuse of stock footage.
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