Elaine is awakened by an alarm clock and when she looks at her clock, it is 3:30. She then realizes that it's her neighbor's alarm clock and when she bangs on the wall and tosses and turns in bed, her clock now reads 3:29.
When Kruger shows the airbrushed photo to George to show the mole hasn't grown, George is still in the photo.
When George is showing the airbrushed photo to Jerry back in his apartment, Jerry is holding the photo in his hands. After a camera angle switch, the photo is now on the coffee table, but it's not the airbrushed one he had in his hands -- it's the original one with George in it.
When Dr. Sitarides storms out of the exam room, she goes from the door to halfway across the hall in an impossibly short time.
Dr. Sitarides asks Jerry if he thinks that she "infected" him with hives. However, hives in and of itself is not an infection.
Elaine and Kramer use the slicer to slice meat for the cat in the next apartment, even though there is no electricity in the building.
When Elain's neighbor shorts out her electricity while she's on the phone. She loses
her connection on the phone. Since it's the 1990's, Elaine has a landline that would
not be affected by a power failure. The only thing phones needed electricity for in
those days was caller ID and that usually came from AA battery.
The telephone Elain was using was cordless and cordless telephones will not send or receive calls without electricity so what happened with the telephone was correct.
When Kramer short-circuits Elaine's neighbor's circuit to turn off the alarm clock, he puts a paper clip in the receptacle, which produces no spark and the lights flicker a bit before turning completely off. In reality, if the lights and the receptacle were on the same circuit, short-circuiting the receptacle would produce a massive spark and the lights would turn off immediately with no flicker.
Midway through the episode the coat hook in Jerry's apartment disappears but the screw holes in the wall are visible. Presumably it was removed to accommodate Kramer's physical comedy when Jerry tosses him the container of metal cleaner and contaminated towel.
Although computer photo correction was already being used in the 1990s, it's previously stated that the photo will be airbrushed, not digitally retouched.
The camera that George hands Kramer to take a picture with Kruger with is motorized - that is, it advances the film itself after a picture is taken (there is no winding required). It is also a viewfinder (non-SLR) camera. However, when Kramer shoots Kruger's picture, we hear what sounds like a reflex mirror and no film advance.
During George's (Jason Alexander) flashback, which is set in 1989 - the year of episode 1.0 Good News, Bad News (1989), George is depicted with a full head of hair, but in the actual first episode of the series he is starting to bald.
At the end, when Kruger points the photo out to George, he says it was taken "ten years ago." According to George, the incident occurred in 1989 (so that's when the photo was taken). This episode aired in 1997.
Kramer says "I think we're looking at half a millimeter" when he is examining Elaine's neighbor's door. Presumably, he is referring to the clearance between the door and the floor. Yet we can see the clearance, and it is about a centimeter (ten millimeters).