The Cosby Show (1984) - 14 mistakes in entire show

Revealing: Everytime someone opens the front door to go outside there is just steps leading outside, but when they are on the steps outside and the doors to the inside are open there is a wall and a table with a lamp. Inside that is not there.

Other: The outside shots show that the house is in the middle of a row of houses, connected to other houses on both sides. But in the living room, behind the stairs, is a window looking outside. There couldn't possibly be a window there as that is where the house shares a wall with the house next door.

Factual error: In season 2 episode "Denise's Decision", Cliff says he went to Hillman college because his wife Claire was going to go there. But in the season 4 episode of "The Prom", Claire and Cliff both state that Cliff was away at Hillman studying for finals, during Claire's prom. That would mean that Cliff would have attended Hillman first, and that him going to be with Claire would be false.

Continuity: The father was known as Clifford in the beginning but the name was changed to Heathcliff (you can see this on the nameplate for his office).

Deliberate "mistake": In the very first episode, the kids are fighting and arguing all throughout the house. Claire then asks Cliff, "Why did we have 4 kids?", referring to Denise, Theo, Rudy, and Vanessa. In all of the following episodes, they actually have 5 kids. I guess they decided to add Sandra (the oldest Huxtable) later down the road.

Continuity: After Cliff talks to Peter, Theo is told to run to the neighbors across the street. However, he can be seen in the background of some shots when the twins do their game. As soon as the twins finish, Theo is shown coming back into the house.

Continuity: Cliff says "a young trumpet player while sitting in the bandstand watching the dancers". But in all the later episodes, Russell plays the trombone, and he had been for a long time.

Continuity: In this episode, Rudy is riding her bike around the house which is right on the corner of a block. Since when is their house on the corner?

Continuity: 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.

Continuity: 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: 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.

Visible crew/equipment: Early in this episode, as one of the couples walks through the kitchen door into the living room, you can see a hand on the door pulling it closed.

Factual error: When Olivia (or whoever) is teaching Russell how to play the Nintendo game she tells him the controls and includes "C and D". The old Nintendo system had no C or D.

Plot hole: When Theo is complaining that his father is inviting too many people to his graduation, he says "I saw him in the backyard 5 minutes ago hosing down the beach chairs", but this couldn't have been possible because in fact, Cliff was upstairs right before that scene, and then went straight to the living room, so there's no possible way that Cliff could have been in the yard at the time Theo had said he was.