Continuity mistake: In season 3, "Lucy and Ethel Buy the Same Dress", when Ethel comes out of her bedroom wearing the dress she had told Lucy she'd return, Fred calls her "Ethel Louise." In season 3, "The Million Dollar Idea", when Ricky tells Lucy and Ethel that it will cost them twenty cents to mail each dressing jar, Lucy takes Ethel by the hand and calls her "Ethel Roberta." In season 4, "Ethel's Hometown", throughout the episode Ethel is called "Ethel Mae."
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.
Continuity mistake: The step up into the kitchen is no longer there in later shows such as "The Fur Coat" and others.
The Séance - S1-E7
Continuity mistake: After Lucy tells Mr. Merriweather that he's invited to the seance, when it cuts to Lucy unfolding the card table legs, note the couch behind her with one normal seat cushion on the left, but in the next wideshot there's an additional shorter cushion under the normal cushion. The small towel also repositions itself neatly on the couch. (00:11:55)
Lucy Is Jealous of Girl Singer - S1-E11
Continuity mistake: When Ethel walks in while Lucy's vacuuming, Ethel has the folded newspaper under her arm and there's only small print on the paper, but after Lucy offers Ethel a cup of coffee now the headline can be seen on the still folded paper under Ethel's arm. Then, when Lucy unfolds the paper we see both the front and back page filled with pictures and the headline, but that area of small print which was seen in the earlier shots does not exist on either side. (00:00:40)
Continuity mistake: When Lucy crawls into the New Neighbors' apartment she's startled by the stuffed bear head, and in the closeup of the bear head it's in front of a bare wall, but in the rest of the shots it's in front of furniture. Additionally, other things change as well between shots: the books under the bear, the hat, etc. (00:10:15)
Continuity mistake: After spending the night at the hotel, when Ricky goes to the front desk to speak with the "Justice of the Peace" it's 7:30 on the wall clock. Then, when Mr. Willoughby stands by the stairs and calls to his wife it's almost 7:40, but when Ricky gets ready to propose it's 7:30, but it's 7:45 when Mrs. Willoughby comes downstairs in the closeup, then back to 7:30 in the wideshot. (00:17:40)
Continuity mistake: When Lucy handcuffs herself to Ricky we see the style of handcuffs as they phone the locksmith, but when they're both in the bedroom their handcuffs are entirely different, then their handcuffs revert to the original style when the locksmith shows up. Additionally, when Lucy cuffs Ricky's wrist note the direction of the locking bar around Ricky's wrist, but the next morning when the locksmith is with them, the locking bar is around Ricky's wrist the opposite way, which is quite impossible. (00:06:45)
Continuity mistake: After everyone comes out of the judge's chambers, the door goes from open to shut repeatedly.
Continuity mistake: Here it's said by the Ricardos that Fred and Ethel have been married for 25 years. Problem is in Season 1's episode "The Girls Want To Go To the Nightclub" the Mertzes both say they've been married for 18 years.
Continuity mistake: While Lucy's taking a tally of who everyone's voting for, the writing on the posterboard changes in Lucy's closeups. (00:14:45)
Continuity mistake: When Ricky sings during the rehearsal, there's a pencil tucked behind his ear with its point facing the back of his head, but after Ricky's song is done and he moves the microphone stand, in the next shot when Lucy walks in the pencil point now faces the opposite way, though Ricky hasn't touched the pencil. (00:19:45)
Continuity mistake: While tired Lucy is trying to open the card table's legs, she lays her head down then falls asleep, and when it cuts to Ethel and Fred walking in on our sleeping Lucy, there's writing on the table's underside which wasn't in the previous shot. (By the markings on the table it also looks as if the table has been turned on its adjacent side). (00:06:10)
Lucy Wants New Furniture - S2-E28
Continuity mistake: At the start of the episode, when Lucy puts the baby in the crib there's only one bumper pad and it's on Lucy and Ricky's side of the crib rails, but in the baby's closeup there's a bumper pad at the rails behind him - which is the opposite side of the crib. (00:00:45)
Lucy Wants New Furniture - S2-E28
Continuity mistake: After Lucy mentions the ad for a couch and coffee table, when she walks over to the desk note the shadow and lighting change on the back of the desk. (00:02:10)
Lucy Wants New Furniture - S2-E28
Continuity mistake: Lucy runs back and forth from Ricardo's and Mertz's apartment through a door in Mertz's living room that is not there in other episodes before or since.
Continuity mistake: At the end of Ricky's song "Lady of Spain" when he sings the verse "all that my eyes are revealing, Lady of Spain", in this wideshot we see Lucy in front of the balcony doors facing forward raising her arms, then in the next side closeup Lucy's still facing forward and a flag has suddenly appeared behind her on the balcony door. (00:21:50)
Never Do Business With Friends - S2-E32
Continuity mistake: In Lucy and Ricky's apartment there are six shutters between the kitchen and living room, a set of three open to the left and three open to the right, but after the washing machine falls off the porch, when Mrs. Trumble's nephew thinks they're all crazy he runs through the back door and we see a set of four shutters on one side. Also note the round knobs are at the bottom corners, when they should be higher up at the center. (The prop shutters that we see through the doorway during the porch's "exterior" shots are identical to the seven shutters that were in apartment 4A, before the Ricardos moved downstairs). (00:22:10 - 00:24:25)
Never Do Business With Friends - S2-E32
Continuity mistake: In this episode, the Mertzes buy the Ricardo's old washing machine and say that theirs is old enough to be in the Smithsonian, yet just a few episodes earlier ("Sales Resistance") Fred tells Ethel to come and see her new Handy Dandy washing machine.
Continuity mistake: When Lucy and Ricky are sitting on the coffee table looking through photos of Little Ricky, just as Lucy quips, "What magazine, body beautiful?" in the closeup the baby's photo orientation is portrait, but in the wideshots when Lucy looks at it and hands it to Ricky the orientation is landscape. (00:01:50)
