I Love Lucy (1951) - 5 mistakes in series 1

Revealing: When Ricky and Lucy are dancing in the living room, the camera swings too far to the left, and the edge of the set wall and the adjoining bedroom set can be seen briefly.

Other: In the scene where Lucy supposedly stumbles on a few minutes before hand because she is drunk from the Vitameatavegamin, you can see a sliver from her living room in the backstage area.

Other: In the scene where Ricky tries to get Lucy to have the drink that will put her to sleep, from the audience's point of view, Lucy is on the right side behind the living room table with the altered drink on the table in front of her. Ricky is to the left with the unaltered drink in front of him. While Ricky is repeating Lucy's spinning/clapping movement, Lucy switches the glasses around. When they are done dancing, Lucy ends up behind the table to the left, with the altered glass again in front of her. Ricky points to the wall and tells Lucy, "That is the biggest spider I have ever seen!" While Lucy is examining the wall, Ricky switches the glasses back around. The unaltered glass is now in front of Lucy. She then proceeds to drink while Ricky smiles at her plan's apparent "failure". If you have watched the glasses carefully, you will realize that Ricky is actually the one who ends up with the altered drink, not Lucy.

Visible crew/equipment: Just after Lucy does her ballet "audition" for Ricky, the microphone dips into the shot above their heads.

Revealing: In the last scene of the episode, just after Lucy pulls a gun out of the guitar case, you can see the living room table has been propped up on 4 blocks to make it taller.