Equal Rights - S3-E3
Revealing mistake: When Lucy and Ethel go down to the jail house to see Rickey and Fred, there is a scene where Lucy says "I wonder how he (Rickey) kisses" and then she kisses him, then Ethel says the same thing about Fred and leans in for a kiss. Problem is she obviously doesn't get anywhere near his lips to touch them for a kiss, yet makes the kissing sound, turns around and says "hmmm" as if the "kiss" wasn't all that . Of course we all know those two characters did not get along on set anyways .
Revealing mistake: When everyone is examining the car that Fred bought, during a shot showing the front of the car, everyone's shadows are falling on the "street" behind the car, making it obvious that it's a painted backdrop.
Continuity mistake: In the episodes where Lucy and Ricky are Getting Ready to move to the country, there are shots in the Ricardos' bedroom that shows a wall on the right hand side of the room. In previous episodes, there was a window where the wall appears during the later 'moving to Connecticut' episodes.
Continuity mistake: After everyone comes out of the judge's chambers, the door goes from open to shut repeatedly.
Lucy Gets a Paris Gown - S5-E20
Visible crew/equipment: Lucy is walking around the living room, assembling a sandwich from food she's hidden in various places. When she tells Ethel that they're low on lettuce, the shadow of the boom mike is visible behind her.
First Stop - S4-E14
Revealing mistake: When the bed Lucy and Ricky are in moves as a train goes by look real close and you can see the wheels on it to help move it across the set piece.
Suggested correction: Not necessarily an error. My bed frame is on wheels.
The Operetta - S2-E3
Revealing mistake: Near the end when the repossession men are taking away the costumes and scenery, as they are removing Ricky's pants one of the chorus members can be seen waiting backstage for her cue to enter screaming.
Character mistake: Bob Hope mistakenly calls Lucy "honey" when she's dressed as the intrusive hot dog vendor. He was supposed to believe she was a man. (00:12:00)
Don Juan and the Starlets - S4-E18
Visible crew/equipment: After Fred fibs to Lucy about Ricky spending the night, when Fred walks over to the door just as Ethel walks in, we can see the shadow of the boom mic moving at the top, right corner of the screen. (00:18:30)
Bonus Bucks - S3-E20
Continuity mistake: After Ricky takes out the extra expenses from the prize money, when starched-up Lucy walks into the office Fred's holding the last dollar bill, and in the closeup of Ethel's and Fred's shocked reactions to Lucy's appearance we see Lucy's hand holding the dollar, but in the next wideshot Lucy's open hand is empty so Fred gives her the dollar. (00:24:35)
Ricky Asks For a Raise - S1-E35
Character mistake: After Tropicana nightclub owner Mr. Littlefield replaces Ricky Ricardo with Xavier Valdez, "the Konga King," Lucy, Fred and Ethel try to get Ricky's job back by going to the nightclub in a succession of different wigs and costumes, then leaving when they learn that Ricky is no longer performing there. At one point, Fred and Ethel enter the nightclub, posing as "Mr. And Mrs. Crumley." A disguised Lucy enters one minute later and is outraged to hear that Ricky is no longer there. Ethel then pretends to phone a friend to tell her to not come to the nightclub. Lucy says, "Attagirl, Mrs. Crumley." However, when Ethel had told the maitre d' she had a reservation for "Crumley," Lucy had not yet entered and therefore should not have known that name.
Suggested correction: During the point when Mrs. Crumbley wants to call her friend to get her friend to cancel her reservations as well, Mr. Littlefield says, "But Mrs. Crumbley," to protest as she walks to the phone to make her call. So he did say her name in front of Lucy, thus giving her the name to reply with, "Attagirl, Mrs. Crumbley."
Lucy Wants New Furniture - S2-E28
Deliberate mistake: Lucy and Ethel try and hide the new furniture in the kitchen so Ricky won't find out about it. This in turn forces Lucy to run through the Mertz's apartment to retrieve items from her own kitchen when Ricky wants them. This is supposedly done because the furniture blocks the doorway and is wedged in place thus preventing them from using the door. However it is quite clear that there is a lot of room for the furniture to be pushed into the kitchen and not block the door. They say it is wedged on the sink but there is a lot of room on the other side by the cupboards, along the back wall.
Audio problem: About 6 minutes in, a friend of Fred comes to the door and Ricky answers it. The man says Mr. Cardo instead of Mr. Ricardo, but Ricky says yes anyway.
Little Ricky Gets Stage Fright - S6-E4
Continuity mistake: In the first 5 minutes of the episode, the necktie of Fred Mertz changes length several times. Sometimes it touches his belt, in other times, both ends are the same size. (00:02:00 - 00:03:20)
Lucy in the Swiss Alps - S5-E21
Other mistake: The Ricardos and Mertzes are trapped inside an abandoned cabin after it is buried by an an avalanche. They are rescued by an oom-pah band playing "La Cucaracha." When the band members enter the cabin, their clothes and shoes are completely dry, and they don't track in any snow or water. Then when the Ricardos and Mertzes follow them out of the cabin, they leave their backpacks behind.
Lucy Has Her Eyes Examined - S3-E10
Other mistake: When the eye doctor has Lucy repeat the same letters on the eye chart that she claims Ricky got all wrong, she repeats the same letters out loud, then moves closer to the eye chart and repeats the same letters out loud, then pauses in error when she read them all off correctly: P E C F D.
Vacation from Marriage - S2-E6
Other mistake: The camera jostles badly when Lucy steps up on the board to cross the plank.
Visible crew/equipment: At the very start of the opening shot, when Lucy is at the stove, there's a visible crew member at the right side of the screen.
Continuity mistake: At times Ricky wears his gold wedding band, and other times - especially at the Tropicana - it is missing from his finger.
Suggested correction: So he took it off while performing. I googled images of Desi and Lucy and you can see he wore a wedding band in real life. Therefore, taking it off while filming would have been a deliberate choice. It's only a mistake if the band appears and disappears within a scene.
The Adagio - S1-E12
Visible crew/equipment: Crew member shadow is visible at the foot of Ricky's bed near the end.