The Great Train Robbery - S5-E5
Revealing mistake: When Ricky and Lucy find their train compartment, while they stand outside their door talking we can see the actor playing the porter peeking out of the next compartment's door waiting for his cue, and in a few moments he opens the door just as Lucy approaches. (00:02:20)
Homecoming - S5-E6
Revealing mistake: In the scene in the Ricardo's kitchen, after Fred enters through the rear entrance the door is left open. Through the doorway one can see at a certain point, not just the NYC real estate in the distance but apparently a blown-up photograph of what "appears" to be a man and woman sitting at a small table in a cafe. However, in a subsequent episode of the same view through the rear door it appears that the exact same background photo shot may actually be, not a man and woman but features on the outside of a building, such as one or more windows.
Revealing mistake: While Lucy is out on the ledge, if you look at the pipe as it runs from above the ledge to below it, the two pieces of pipe don't line up. They are off about the full diameter of the pipe. Also when the pipe pulls out, it's obvious the pipe is on a hinge at the bottom and not really attached to the lower pipe. Later, there is also no stream of water falling from above where the pipe was supposed to be connected as a drain even though it is pouring out.
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.