Continuity mistake: At the end of the episode, Theo and Cliff are drinking a soda. Cliff pours half of his in a glass and begins drinking it. When the camera pans for the end of the episode, the bottle that cliff set down is once again full.
Rudy Spends the Night - S3-E14
Continuity mistake: Cliff puts a paper bag on the counter facing away from him, when Theo leaves it is suddenly facing the other way.
Continuity mistake: In the scene where Theo tries to prank Cliff, and Theo grabs the fake gum, he stuffs the "Bag 'o' Gags" under his shirt. You can see throughout the scene that Theo is holding up the bag with his hand. Later on in this scene, the bag drops. In the next shot, there is something green showing from underneath Theo's shirt (The Bag 'o' Gags). Then in the next shot it is hidden again, being held up by Theo's hand. (00:03:55 - 00:05:55)
Continuity mistake: There are two jackets hanging (one pink on top of one blue). When we see Vanessa and her friend, Janet, fighting Theo to get through the door, the pink jacket obviously falls down. When Dr. Huxtable comes in, the jacket is seen hung up again, but when he leaves, it is on the floor again.
Twinkle, Twinkle Little Star - S4-E15
Continuity mistake: In the opening scene, Vanessa pours a full glass of milk. In a shot a few seconds later, she is pouring the same glass about 1/4 full.
Waterworks - S4-E18
Continuity mistake: Rudy blows bubbles in her milk and the bubbles rise above the glass. The shot changes to Vanessa and when it goes back to Rudy the bubbles are gone.
Continuity mistake: Cliff and Clair are talking in the living room while Cliff is making a sandwich. As Clair asks Cliff if he would trust her with a sexy man, Cliff starts putting potato chips on his sandwich from a bowl. As he takes the chips out of the bowl, the level of chips goes down. When Cliff asks Clair if she would trust him with a nineteen year old woman, the bowl is miraculously at the level it was at the beginning of the scene. But as Cliff finishes talking, the bowl is back to it previous level.
Mrs. Huxtable Goes to Kindergarten - S5-E14
Continuity mistake: In the previous episode they got a new couch, in this episode the old one is back.
Continuity mistake: When Vanessa and Rudy are at the table, the amount of orange juice in Rudy's cup changes a couple of times.
Denise: The Saga Continues - S6-E1
Continuity mistake: Cliff puts his tool belt on the couch behind Denise - there is a hammer that changes position between shots.
Continuity mistake: A root beer comes down the tube and Theo catches it. In the next shot Cliff now has the root beer. Also there are 2 root beers sitting on the table, then suddenly Theo and his friend are holding them.
I'm `In' With the `In' Crowd - S6-E3
Continuity mistake: When Vanessa calls home and Denise picks up the phone, there is a cord attached to it. At first it's behind Denise's hand, then it's in front.
Denise Kendall: Babysitter - S6-E6
Continuity mistake: In the scene where Bob gives Elvin the apple cider and another jar, when you first see the two jars, the jar in his left hand has a few inches of foam on the top. Bob sets the jars on the table, and the foam is gone. When the shot returns to the table the foam is back again.
Continuity mistake: When Cliff returns from the store for about the fourth time and the eggs and tomatoes fall out of wet bag onto the floor why aren't the eggs in a carton? The bottom of the bag drops out, so the carton can't be in the bag.
Continuity mistake: When Pam is in the office talking to Cliff and he tells her about the curfew time, she has a pencil in her hand and a pad in her lap. In the next shot, Cliff offers her a pencil and tells her to take the pad (which is on his desk).
Continuity mistake: Theo walks into the living room eating a banana and holding an apple - he eats the banana throughout the scene. At one point he starts eating the apple, the banana peel disappears, and a mandarin orange appears on the couch next to him.
Continuity mistake: When Theo and his parents are talking in the kitchen, there is a box on the table. The cover is on and Theo is standing in front of the table, the next shot he is standing next to the table leaning on a box and the cover is off.
Continuity mistake: When Theo walks into the kitchen, there are two half gallons of chocolate milk on the stove. When he sees the milk and picks it up there is only one. Theo places it on the table, later the second one reappears on the stove, before he leaves Clair gives him the one that is sitting on the stove, and the one on the table disappears.
Continuity mistake: When Jake is describing the accident, he takes some glue tubs from the counter. Partway through the scene they change to glue bottles.
It's Apparent to Everyone - S8-E6
Continuity mistake: When Russell and Olivia leave, a stuffed animal appears on the table by the truck. When Clair comes in the stuffed animal disappears.
Chosen answer: That is the song "Open the Door Richard."