The Fatigues - S8-E6
Continuity mistake: At the start of the episode, Cynthia is drinking a glass of wine. While speaking near the end of the scene, she is holding the glass in her right hand and says, "You know, guides you in your career path." The next shot is of Jerry and instantly the glass has disappeared from her hand with her right hand resting on the table. You can also see the glass is closer to her left hand now.
The Checks - S8-E7
Continuity mistake: When Jerry is showing George how he twirls the umbrella in his apartment, it has distinctive bright red and yellow stripes. He sets it on The Couch and then Kramer accidentally sits on it. It is now dark colored.
Continuity mistake: When Kramer spills the tomato juice all over Jerry's walls, he grabs a light colored oven mitt to wipe it off. In one shot he wrings out the sopping mitt over the juice pitcher. When the shot changes and he tosses the mitt back onto the counter, the mitt is still the original color with no hint of red stains.
Continuity mistake: Due to the effect of the red glow on Kramer's eyes, he confuses the pitcher of tomato juice from Jerry's refrigerator for a pitcher of milk, pours it into the cereal, then gags and promptly tosses the contents of the bowl into the trash beside the fridge. In the close-up he tries to wipe some of it off the wall, but there's still a huge red mess left on the wall, in the trash, etc. In the next wide shot of Jerry and Kramer, the trash and wall are spotless.
Continuity mistake: When Newman is first eating the chicken in Seinfeld's apartment, the amount of meat on the leg changes without Newman putting down the leg and getting another one out of the box.
Continuity mistake: After crazed Jerry and Elaine leave to get a hat, Kramer picks up the tub of ice cream Jerry had set down and starts to put the lid on. In the next shot, he's not holding the ice cream.
Continuity mistake: In one scene George is solving a Rubik's cube in Jerry's apartment. When he leaves, he places the cube on Jerry's kitchen counter, and it is in the middle of the counter with the red color facing out. In the very next shot, it is moved much closer to the far edge of the counter and the color facing out has changed.
Revealing mistake: When Kramer and his lawyer, Jackie, are in the taxi; when Jackie says "who told you to have a pow wow", a man is seen walking across the rear window. The taxi is supposed to be moving, but the man's position stays the same (the taxi should be pulling away from him). The actual traffic filmed for the green screen doesn't seem to react to a man jaywalking in front of them either, as it was someone walking across the set.
Continuity mistake: After George and Jerry discuss the fact that George will never have sex again, they stand up to leave the coffee shop and George places a large book under his arm. In the very next shot, he is holding the book in both his hands.
Other mistake: The tenant board member tells George that Mr. Eldrige in apartment 8C has decided he wants the new apartment. However, the new apartment in question has a 3-digit number - 808 I believe. This indicates that the building would not have single digit numbers and letters (Such as 5E, 8C, etc.) as part of its numbering system.
Factual error: The grocery store that Kramer walks into with Little Jerry has a round doorknob. Those were phased out of public use in 1992 after the Americans with Disabilities Act took effect, but this episode takes place in 1997. (00:09:45)
Audio problem: When Kramer is telling Jerry about Little Jerry as he exits The Apartment, Kramer finishes his sentence with the word "jealous", and the S is audibly cut off in the middle, as if the audio was spliced there. (00:14:25)
Continuity mistake: When Celia breaks out of prison and comes to George's apartment, George opens the door and starts talking with her. After George says "And you decided to pop in" the shot shows Celia but the door has now closed behind her. It would have been impossible to close without us seeing it because Celia would have had to have moved forward to close the door.
Factual error: On the bottom of all checks, they have the routing number, followed by the account number, followed by a repeat of the check number found in the top right corner. When we see Jerry's bounced check, "1246" isn't seen after the account number.
Continuity mistake: The exterior of the video store in the episode looks different from the interior. From the inside, we see a neon "open" sign on the window and other writing, and also no exit sign on the door, all of which is contrary to the outside view of the store. (00:09:25)
Continuity mistake: When Morty's exercising first wakes Kramer up, his clock reads 5:30. Then in another shot, the clock reads 5:26. (00:10:05)
Continuity mistake: We find out George's parents sleep in separate beds. His father says "Thirty years ago we came to an agreement. It was the only way I could get some rest. Estelle's got The Jimmy arms." This contradicts S5E10, "The Cigar Store Indian", when George's parents come back from their trip, Estelle finds a condom wrapper in "our bed." Also Frank asks George, "You were having sex on our bed?", and Estelle follows by saying, "Who told you you could have sex in our bed?!" (00:16:50)
Continuity mistake: In the episode "The Suicide", Kramer discusses suicide with Jerry, and says that he'd give someone 72 hours to come out of a coma before all his property is up for grabs. However, in the episode "The Comeback", Kramer tells Jerry that he never knew that people could come out of a coma.
Continuity mistake: Towards the end of the episode, it transitions between the Yankee ball at night and "Susie's" wake which is during the day.
Continuity mistake: When Mike accuses Jerry of murder at Susie's wake, watch the people behind and around Jerry. There are women either side of Peggy, turning around, looking surprised and moving their hands. The next shot, we see Jerry from behind his seat, and everyone has instantly changed to sitting perfectly still, looking ahead with their hands still.
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.