The New Neighbors Meet the Addams Family - S1-E9
Revealing mistake: As the Petersons look at the square of carpeting coming up, the wire pulling the door up is visible.
Other mistake: As Fester goes to shoot Gomez, his aim strays upward to about a 45 to 50° angle. Not enough to shoot the support chain on the light that is directly above him, and hits him on the head.
Continuity mistake: As Fester gets a pistol from the drawer, there is an assortment of items in the drawer, and he leaves it open. A moment later, he goes to exchange guns, the drawer is closed and suddenly bare, except for the other pistol.
Continuity mistake: As Fester talks with Gomez, he has a fork in hand that has a small chunk of meat on it. In one quick take, there is an entire meatball on it, then a moment later, it's a small bite again.
Morticia Joins the Ladies League - S1-E6
Continuity mistake: As Pugsley comes out of the closet counting his money, he's dropping coins from his right hand to his left. A second later, it's reversed, and his facial expression changes in the same moment.
The Addams Family Meet the VIPs - S1-E11
Revealing mistake: As Morticia and Gomez throw the knives at the target, and they stack tip to hilt, we can see the wire they slide on.
The Addams Family Meet the VIPs - S1-E11
Revealing mistake: After Mr. Harris leaves the play room, Fester goes to lay down on the bed of nails. As he does, the squared outline of the board under his robe he lays on is visible.
Morticia and the Psychiatrist - S1-E2
Visible crew/equipment: When Uncle Fester climbs down the tree (after observing Pugsley interact with the shrink, a shadow of the moving dolly mic is visible as it moves backward. (00:22:35)
The Addams Family Goes to School - S1-E1
Visible crew/equipment: When the phone rings and Thing hands it over to Morticia, the camera zooms out and you can the actor playing Thing quickly hide behind the couch. (00:24:15)
Morticia, the Breadwinner - S1-E26
Continuity mistake: As Pugsley tells Wednesday about satisfied customers, his arms are by his sides, then suddenly crossed.
Continuity mistake: As Fester talks with Gomez, he puts the fork with hamburger on it down in the bowl he's holding, and his right hand under the bowl. A second later, he's suddenly holding the fork.
Other mistake: As Kitty comes down the stairs, Hilliard screams, and Kitty goes back up. It's obvious the film was run backwards.
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