Audio problem: When Cliff asks Rudy what's her boyfriend's name, you can hear a man off-camera saying "Bud" before Rudy answers.
War Stories - S3-E11
Continuity mistake: Towards the end of the episode, Cliff Huxtable is sitting in the living room with his father Russell, Sgt. Stokes, and Homer. He is telling them of an incident that happened while he was in Bermuda. He is using dominoes to explain his story. At first there are about six or seven dominoes standing up on their sides. The camera angle switches, and all the dominoes are flat on the table. It goes on for a minute or so with the dominoes lying flat on the table. Then when Russell, Sgt. Stokes, and Homer get up to go for a walk, the dominoes are standing up again.
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)
Revealing mistake: Rudy snatches a hat off Kenny's head and she says the line: "Gimme back my hat Bud!" At same time, you can see the actor who plays Kenny silently mouthing the line with her. (00:12:50)
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.
Continuity mistake: When Vanessa walks down the steps and drops all her papers, they are shown on the steps, then off the steps and then on again.
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: Cliff takes the empty orange juice carton out of the fridge and puts it on the stove. When Theo comes in it is now on the counter next to the stove.
Continuity mistake: When Rudy comes down the stairs and wants a lemon, Cliff is cutting one. In one shot it is fully cut. He givers her a piece of one he had cut earlier. When Rudy leaves suddenly he has a uncut lemon in front of him that he cuts.
Chosen answer: That is the song "Open the Door Richard."