Continuity mistake: When Jerry's sitting with George in the hospital talking about George's jacket, as Jerry says "no, I tried it on, it fits good", he's gesturing with his left hand, which he then puts in his lap. From the reverse angle though, his left hand's still raised, then he lowers it again.
Continuity mistake: During his odd holistic visit, Tor puts both the middle finger on George's temples. New shot, and he is using 2 fingers. (00:14:40)
Continuity mistake: The belligerent paramedic shouts at the driver "I want that Chuckle back, do you hear me?" pointing a finger at the opening, but his arm is on his own leg in the following shot. (00:18:10)
Continuity mistake: George grabs the slip of paper from Elaine's hand. When he has his 'heart attack', in the shot when Jerry says "What does that mean?" the paper goes from his left hand to his right hand. (00:02:45)
Continuity mistake: Elaine hands the ice cream bucket to George. George is holding the plastic spoon against the container, in his left hand. In the close-up he reaches for the spoon off-camera with his right hand. (00:20:45)
Continuity mistake: Elaine and Jerry guessed that George is telling them about a heart attack. Jerry says "I know what this is" pointing a finger - but in the next shot not only the hand is pointing a finger; the hand is holding the yellow note. (00:03:05)
Continuity mistake: Jerry is smothering George with the pillow when Elaine walks in. First shot and a black nurse is walking behind her. Cut for one second to Jerry, back Elaine and the same guy is still walking, exactly where the view cut the first time. (00:06:25)
Continuity mistake: Elaine walks up to George in bed, and she asks him if anyone's got his apartment yet. For the brief part of dialogue about the zen lifestyle thing, the top sheet is rolled up in a noticeably different way from the rest of the scene. (00:07:00)
Continuity mistake: On his deathbed George triumphantly utters "There's nothing wrong with me!"; the doctor cools his enthusiasm down though, saying that he wouldn't go that far. His hands are crossed in front of his body - at the cut though he's suddenly already browsing through George's medical file. (00:08:10)
Continuity mistake: The doctor is examining George. George yells into the stethoscope so he takes the buds off his ears. Not just that; he removes the instrument and puts it around his neck. George then freaks out and starts naming various odd and even rather harmless conditions; the doc is wearing the stethoscope again. Flirting with Elaine you can see the instrument sorta shuffles around, with part of it exposed and part of it under the scrubs' collar, now the left side, now the right side. When Jerry breaks off their idyll with the Romeo and Juliet reference, the stethoscope is back around his neck, only to be again in use when George asks "With a knife?" (00:08:00)
Continuity mistake: When the doctor tells George that he can have some ice cream, he touches his arm. Difference is, in the first shot the clipboard is in the right hand, in the close-up it's in the left hand. (00:09:20)
Continuity mistake: Tor is introduced; in the reaction shot on Jerry and George to the weird hug with Kramer, Jerry is holding his own leg with his both hands. In the wider shot he just uses his left and with nothing else in it. (00:13:30)
Continuity mistake: During the visit, whenever George asks questions about hot water (can I use it on my face, can it be lukewarm) his hands have a sudden position change between shots. (00:14:50 - 00:16:00)
Continuity mistake: Jerry gives Tor the piece of paper to decipher; the paper is curled towards him in the reverse shots, and Tor's hand is placed at a different height - just look at the fold. (00:17:30)
Chosen answer: George does mention his brother in the episode "The Parking Space". They actually really never mention anything that contradicts the fact he had a brother though, it just isn't mentioned.