Continuity mistake: At the beginning of the show, when Jerry is having a massage, his hands are in front of him, under his chin. The position of his fingers change considerably after The Masseuse says, "I don't know" but then return to the original position in the next shot.
Continuity mistake: While Jerry is having his massage, The Masseuse walks around the table to reach his right side and we can then see two items of clothing, one blue and one grey, hanging on the clothes stand behind them. During the rest of the scene, we only ever see the grey item hanging there.
Continuity mistake: Jerry is waiting for George to come into his apartment and he says to Elaine and Kramer, "my oldest friend is dating the governor", and then folds his arms. In the next shot, as George comes in, Jerry is suddenly holding a glass of juice - there was no time for this change to happen naturally.
Continuity mistake: When Morty is giving Jerry directions to the scuba diving site, The Pen alternates between being in Morty's hand and on the table between shots.
Revealing mistake: While Jack is leaving The Apartment after giving Jerry The Pen, you can see they have put a fake background outside the front door. What's more it is not even that realistic. It looks like a forest with a river in the middle. The Seinfeld's Florida apartment is situated amongst many other apartments around it.
Continuity mistake: Shot shows a DC-10. Next shot is the inside of a plane that is not a DC-10. Only one aisle. DC-10s have two aisles. (00:00:35)
Character mistake: When George and Elaine go to the coffee shop after The Movie without Jerry, they establish that Elaine moved to NYC in 1986. Then they make fun of the way that Jerry throws up; both imitating Jerry. The "Dinner Party" episode is after the "The Dog". In the "Dinner Party" episode, Jerry brags that he hasn't thrown up since June 29th, 1980. The black and white cookie ended this streak. Elaine would not have been around to see this, not arriving in NYC until 1986.
The Library - S3-E5
Continuity mistake: When Bookman is lecturing Jerry in his apartment, he picks up a navy book with gold lettering and places it on the bookshelf in front of a pink book. For the rest of the shots, the navy book disappears and the pink book is back in front.
The Library - S3-E5
Character mistake: When Marion mentions Mr Bookman she says he'd been on the job for 25 years. Yet later on he tells Jerry he's been on the job since 1971, which in 1991 makes it 20 years.
Visible crew/equipment: After Jerry, Elaine, George and Kramer walk out of the orange stairwell, there is a shot as they come out the door. A car drives past. The crew is reflected in the window.
Continuity mistake: In the first scene (approximately 3 minutes in) where Jerry points out the red-headed woman in The Parking Garage to George, she is leaving her vehicle in a section of the garage that is labeled 14 with a green background. However, later (approximately 23 minutes in) she is shown returning to her car in section 14, but the color is now yellow.
Other mistake: While Jerry is looking out the window, to his right, there is a Yankees baseball cap on top of his mini basketball hoop, above his computer monitor. Jerry in real life is a Mets fan, and he alluded to being a Mets fan on the show as well (taping a Mets game, wearing or showing Mets paraphernalia). In no universe would a Mets fan have a Yankees cap on display and vice versa. This was before George got the job at the Yankees so that can't explain it. Was it just bad set design and props? (00:14:22 - 00:15:30)
Suggested correction: There's a Yankee hat in many previous episodes. It's never mentioned where it came from, but it could be a gift or signed or hold significant value to Jerry as opposed to him buying himself a Yankees hat to put on display. And that's assuming Jerry in the show is such a Mets fan that he wouldn't like the Yankees as well.
The Nose Job - S3-E9
Revealing mistake: When George is talking to his girlfriend about the possibility of getting a nose job, Elaine is visible in the other room waiting to make her entrance.
Continuity mistake: Jerry and George are at the pharmacy. As George pays the bill and is heading out, behind Jerry there's an old lady at the counter. The camera changes and the same lady disappears and you can see her in other side of the store heading again to the counter. (00:02:25)
Other mistake: When Jerry, George and Elaine go out to Long Island to the party, George sees his lady co worker friend who says "guess what property I just sold...129 West 81st". That is Jerry's own address, which wasn't sold to anyone.
Continuity mistake: While Kramer is explaining about being in the Woody Allen movie, George is in the background looking out the window trying to stop car alarms with his keys. Less then five seconds later, George ends up by Jerry's counter (without being seen) and has a can of Shasta in his hand. (00:08:40)
Continuity mistake: While Kramer is on the phone with the guy who stole Jerry's car, a NY Mets hat is seen upside down on the behind George. When Kramer hands the phone back the hat is now right-side up and facing the camera.
The Red Dot - S3-E12
Continuity mistake: After Elaine unwraps her cashmere sweater, Kramer wraps the ribbon around his neck in a scarf-like way and then lies back on The Couch. In a long shot of The Apartment (as Elaine exits the bathroom), the ribbon is gone, but when it cuts to Kramer and he asks about The Red Dot (and for the rest of the scene), the ribbon is back.
