Other mistake: The Kramdens' lock on the door is just a slide bolt that is only operable from inside the apartment. It's impossible for them to lock the apartment door from outside. The Norton's on the other hand have a regular dead bolt lock.
TV or Not TV - S1-E1
Other mistake: At the beginning when Ed tells Ralph he can't afford to buy a new TV right now, he says it couldn't come at a worse time because Captain Video is blasting off to Pluto tomorrow. Ralph gets the idea to buy a set together. When Ed comes down and turns on Captain Video for the launch to Pluto, Ralph yells at him saying they've had this set for three nights and all they watch are Ed's shows. Captain Video should have blasted off for Pluto night one, not night three.
Factual error: When Ralph goes out the window onto the fire escape to save Ed the first time in the episode, Alice is looking out the window (to her right) telling Trixie all the step by step movements of both men, ending with, "and he's taking him right into your window." The Norton's live directly upstairs from the Kramdens, but Alice never changes the direction she's looking at the whole time. She should be looking straight up as Ralph leads Ed into their window. There is no other window to the right. (00:02:30 - 00:03:04)
Mind Your Own Business - S1-E35
Other mistake: Ralph gives Ed the advice to try to "squeeze" his boss for a promotion, but gets fired instead. When Ed comes home, he first stops in to see Ralph but he's not home, just Alice. All he tells Alice is that he had words with his boss and got fired. No details. Ed leaves and Ralph comes home. Alice tells him Ed was fired and described in detail the whole story of him threatening his boss for the promotion. Ed never told her exactly why he was fired.
Answer: It is because Fred's gasoline station was a real place that really existed in the town of Tuckahoe New York. This was where Norton, Art Carney, was living at the time. It was a plug for his friend.
kenykop