Continuity mistake: When "Mulva" is giving Jerry a neck massage, check out the bathroom door in the background. It keeps changing from open to closed.
The Contest - S4-E11
Revealing mistake: In the scene where Jerry and Marla are making out on his couch, at the top right window you briefly notice someone walking by. This is impossible because The Apartment that Jerry lives in is on the fifth floor.
Continuity mistake: In this episode, George asks Russell if his last name contains a "y" and Russel answers that it doesn't. However, Russel is credited in this and subsequent episodes as "Russell Dalrymple."
The Outing - S4-E17
Factual error: Kramer gives Jerry a two-line phone for his birthday, which Jerry plugs in and immediately uses. But a two-line phone requires the installation of an actual additional phone line. What Jerry was using when the NYU reporter overheard him "admitting" he was gay was simply call-waiting.
Continuity mistake: When they initially pull into the handicapped parking space, George is driving a large yellow Cadillac. When they return to see the car destroyed, it is now a much smaller blue car.
Audio problem: As the doctor is explaining how he thinks there were other factors at play to stave off the infection, when he says "something perhaps..." his mouth/lips do not move.
Deliberate mistake: When George is watching Home Alone, the sound effects and music that are heard aren't actually in the film.
The Airport - S4-E12
Factual error: In the episode where Jerry is upgraded to first class while Elaine struggles in coach, the scene changes to show a plane flying with the colors of Southwest Airlines, and you can make out the name "Southwest" written on the tail if you pause as it's landing. Anyone who has flown them knows that there is no first class on Southwest.
Continuity mistake: At the beginning of the episode, the bag on the counter keeps moving and disappearing, and reappearing.
The Implant - S4-E19
Continuity mistake: After George puts a couple of the snacks in his mouth, he takes a bite of the next one before Father Jessup says George is great comfort. In the next shot, the snack George is whole and no longer has a bite taken out of it.
The Trip (1) - S4-E1
Continuity mistake: While discussing Candice Bergen with Jerry, George picks up a menu and places it on the table; both he and Jerry have a menu. In the next shot showing the table (when George says, "I can't believe I missed Kramer,") both menus are flipped: in the first shot, white pages are facing up, and a yellow page is on the back of George's menu as he picks it up; in the second, the yellow sides are facing up. (00:01:02)
Continuity mistake: When Kramer is telling the fantasy camp story to Jerry and Elaine, the suitcase in the background is open different amounts during different shots. (00:09:55 - 00:10:40)
Audio problem: When it cuts from Elaine to Kramer, the audio of what Kramer says is audibly split, as it sounds like he was speaking previously but it was cut off. (00:11:30)
Continuity mistake: After Kramer walks into Jerry's apartment, he shuts the door. However, in another shot a couple seconds later, the door is inexplicably wide open. (00:01:45)
Continuity mistake: During a conversation with Kramer, Jerry is holding a drink in his left hand. Although he is never seen setting it down, the drink disappears in the next shot and he has his arms crossed. (00:02:10)
The Old Man - S4-E18
Revealing mistake: After The Old Man's dentures are destroyed in the garbage disposal, he shouts that his dentist is "downtown." There is sibilance audible in his production of the T sound (after the stop release). Sibilance is high frequency noise cause by turbulent airflow directed at the front teeth vibrating randomly in a small space; if he had no front teeth, there should be no sibilance. (00:14:35)
The Implant - S4-E19
Continuity mistake: During the wake for Betsy's aunt, George puts snacks on his plate while talking to the reverend. He puts at least 6 pieces on his plate while the next shot of his plate shows only 2. (00:14:15)
Continuity mistake: When Kramer enters Jerry's apartment, he closes the door. In the next shot, the door is wide open. A few shots later, George opens the door, which was closed when he entered.
