Other mistake: In some episode Ethel can play the piano and in others she cant.
Vacation from Marriage - S2-E6
Other mistake: The camera jostles badly when Lucy steps up on the board to cross the plank.
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'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)
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.
Lucy Wants New Furniture - S2-E28
Other mistake: When Ricky corners Lucy while she's holding the box of salt, the top and sides of the box have tape hiding its brand name (looks like Diamond), to prevent it from being seen on the air. (00:13:30)
Other mistake: When Lucy tosses the umbrella off the balcony during the Mexican serenade, Ricky somehow doesn't appear to hear it hitting the floor during the pause and keeps on singing. (00:23:30)
Never Do Business With Friends - S2-E32
Other mistake: When Lucy and Ethel are on the back porch fighting about the washing machine and also when Mrs. Trumble walks out, Lucy's back door is open and we can see the shutters between the kitchen and living room, with the kitchen counter/sink underneath, but the sink's faucet which should be seen has vanished. (00:14:45)
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.
Other mistake: When Ricky puts the baby in the crib and begins telling him the bedtime story, in the closeups Little Ricky's sitting up beside the crib rails (at Ricky's side of the room), but in all the wideshots when the camera pulls back to show Ricky's lively storytelling, we can see that Little Ricky is not where he should be.
Other mistake: When Ricky and Fred hold up the newspapers with the big holes in the back page, we see the front page with the headline "Bond Issue Defeated", and it should look familiar since it's the same front page that was used in the episode "Ricky's Old Girlfriend", with the article about Carlotta Romero. (00:18:15)
First Stop - S4-E14
Other mistake: When the Ricardos and Mertzes arrive the first time at One Oak Cabins and Cafe the full moon is amid the tops of the trees. When they arrive the second time the full moon is in exactly the same location amid the tree tops as the first time they arrived. Fortunately, hours later when they make their sneaky escape from the cabin and return to their car the moon is no longer in view.
Other mistake: Lucy walks out on the balcony and sees Van Johnson sleeping on a lounge chair by the swimming pool. The photographic backdrop shows automobiles, trees, mountains, the Roosevelt hotel and many other buildings of Hollywood but when Lucy goes to the pool and sits on the lounge chair next to Van Johnson, the background is just a plain painted backdrop with no cars, trees, mountains or buildings. This plain backdrop also appears in the episode with Harpo Marx.
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.
Other mistake: In the first scene when Ricky staggers down the stairs and on his way to work it's supposedly first thing in the morning but the hands on the Grandfather clock are at 12 Noon/Midnight. (00:00:45)
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 ★