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.
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)
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.
Answer: According to Snopes.com, there is no definitive answer, but the mid-1960s is the most verifiable date with "The Munsters" being cited as the first, although others claim "The Brady Bunch" showed the first couple seen in a double bed. An early TV show from the late 1940s titled, "Mary Kay and Johnny" is also thought to have shown the married couple's bedroom as having a double bed, although probably not with them in it. However, this was when TV was aired live, and there are no surviving episodes, only anecdotal accounts.
raywest ★
Something that is funny is that in the movie "A Christmas Story," they show the parents having two twin beds in their bedroom. In a real situation, they should have shown them having a double bed. Lucy and Ricky had twin beds pushed together in an early episode, which would have been pushing television boundaries in that time.