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: Lucy, Fred and Ethel are admiring the celebrity footprints in cement outside Grauman's Chinese Theatre in Hollywood. In several scenes, the shadows cast by Lucy, Fred, Ethel and a passerby make it very obvious that what appears to be the ticket office, entrance and front wall are actually just a painted backdrop.
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.