Deliberate mistake: In episode "Redecorating" Lucy wins new furniture, then in the next episode "Ricky Loses His Voice" the new furniture's delivered to the apartment, and the new couch has two normal and identical seat cushions. Starting in the next episode "Lucy is Enceinte" until the episode "Lucy Wants New Furniture", in some scenes the couch has the identical short cushions, however, in other scenes one of its seat cushions (depending on the episode, it's either left or right) is much higher than the other. For example, in "Lucy Hires a Maid" the higher seat cushion's on left side while Lucy waits for her lunch, then after Ethel urges Lucy to fire the maid the short cushion's on the left. The uneven cushions are usually seen in scenes with either Desi or another male actor, who sit on the side of the couch which has the higher seat cushion. There are even scenes where both of the seat cushions are the higher ones, such as in "Lucy's Last Birthday."
The Anniversary Present - S2-E1
Deliberate mistake: In this episode Lucy is trying to get Ricky to notice that their anniversary is on Monday the 19th by showing him a large calendar with the 19th circled. However, when they are in California and they celebrate their anniversary and Ricky asks for information to be wired to him, the telegram tells him that their anniversary is on the seventh.
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)
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.
Visible crew/equipment: While Ricky and Fred are trying to clean up the volcanic rice eruption, when Ricky slips on the floor the second time the front edge of the raised kitchen set's platform can be seen. (00:19:15)
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.
Redecorating - S2-E8
Revealing mistake: At the end of the episode, when Ricky and Lucy walk into the bedroom to see the new wallpaper, look behind them when the bedroom door opens and you'll catch a glimpse of William Frawley - waiting for his cue - hiding behind a wall in the background before he ducks back out of sight.
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)
Other mistake: When Ricky is eating out of the can of baked beans, the top of the label has tape hiding the brand name to prevent it from being seen (it looks like Van Camp's). (00:16:50)
Lucy Changes Her Mind - S2-E14
Visible crew/equipment: When Ricky begins to talk to Ethel about the night they all went out to dinner, it cuts to the start of his flashback and it's a closeup of Ricky sitting on the couch calling out to Lucy, and as the camera pulls back into a wideshot we see the shadow of the moving camera/equipment. (00:01:15)
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)
Lucy's Showbiz Swan Song - S2-E17
Other mistake: While Lucy and Ethel are auditioning their act for Ricky at the club, just as Lucy spins around watch her hands as she very quickly pulls on the string at her waist, which causes her pantaloons to loosen and fall to the floor. (00:12:05)
Lucy Becomes A Sculptress - S2-E20
Visible crew/equipment: When Fred steps down from the table hunched over and dressed in his long johns, he walks over to the edge of the couch, and there's an L-shape actor's mark on the floor where he stops and cracks a joke about bowling. Then later, when the art critic tries to lift Lucy's head from the table, more tape marks are visible on the floor. (00:18:15)
Lucy Goes to the Hospital - S2-E21
Revealing mistake: When Ricky, Fred, and Ethel are rehearsing the hospital run, we can see the area to the left and right of the couch, as well as the back wall by the desk. The problem is the telephone cord doesn't actually lead anywhere, it's just coiled up under the couch and not connected to anything. When Lucy says it's time to go to the hospital, Ethel uses the phone to contact the doctor but gets a busy signal, which would be quite impossible. (00:09:55)
Visible crew/equipment: While Ethel's holding Little Ricky trying to soothe the baby, when it cuts to Fred just as he's walking into the bedroom, the sleeve of a crew member and a bit of camera/equipment can be seen at the right side of the screen. (00:03:30)
Other mistake: When Ricky comes home at 3:00 am, the toggle light switch is in the down position. Ricky places his hand over the switch plate and the room goes dark, but the toggle light switch is still in the same down position.
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)
Deliberate mistake: When Lucy makes Little Ricky cry instead of laugh, in the closeup we see the adorable real baby, but when Ricky walks away in the wideshot it's an obvious doll sitting in the crib. (00:01:25)
Visible crew/equipment: After Ricky and Juanita's song rehearsal, when they both join Fred and Ethel at the side table and talk about doing an afternoon performance, the shadow of the moving overhead boom and mic is visible on the wall and curtain, behind Fred and Ethel. (00:17:50)
Answer: There is no reason. It's a just a silly plot device, typical of the era. Women characters were often portrayed as making uninformed assumptions or decisions.
raywest ★