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.
The Statue - S2-E6
Continuity mistake: In The Statue, George claims to have broken a statue that used to sit on his mantle. However, in season 6 episode 3 "The Pledge Drive", George states that he would be a completely different person if his parents had a mantle.
The Busboy - S2-E12
Continuity mistake: At the end of the episode Elaine, George, and Jerry are sitting in the coffee shop and the ketchup moves from inside by Jerry to the outside of the table when Elaine's to-go order is put on the table.
Revealing mistake: In the sequence when he gets shot by the FBI agents for stealing cable, Jerry Seinfeld is wearing ear buds, quite visible when he collapses by the door. Evidently the stage props even loaded with blanks were too loud for his taste. (00:09:00)
Continuity mistake: When George shoos away everyone from The Apartment to make the phone call, in the background you can see the pink bottle with its black lid. When he actually approaches the phone, the bottle is uncapped. (00:09:35)
The Jacket - S2-E3
Continuity mistake: Jerry asks George in front of the fridge "You don't know Robert Schumann?"; between shots his shirt's collar is suddenly fixed, as earlier it was leaving the tie hanging out at the back. (00:05:50)
Continuity mistake: Kramer's moussed up hair looks much different in the first shot compared to the rest of the scene; it's way slicker and frizzles up right after the first cut. (00:00:55)
Revealing mistake: After the scene in which Elaine tells Jerry about her confrontation with the "head-nodding" man, and before the scene where George swallows a fly, the scene cuts to a shot of the exterior of Monk's café. The actual, real-life restaurant used for exterior purposes is named "Tom's Restaurant," and the "m's" in "Tom's" can be seen during this five-second shot. (00:23:00)
Continuity mistake: Jerry says he has never seen an episode of I Love Lucy in his life, then pops the cork on the wine bottle. Then it cuts to the lady and she asks, "Is there anything else about you I should know?" and the wine bottle is still on the table, corked. Then it cuts back to Jerry, and the bottle is still in his hand uncorked. (00:11:40)
The Statue - S2-E6
Continuity mistake: Near the end of the episode, Kramer acts like a cop to get back The Statue. The door is almost completely closed. Just before he leaves, the door is suddenly open about one foot, even though it hasn't been touched yet.
Continuity mistake: Donna's purse strap changes position on The Couch throughout the scene, when she's there when George brings up her liking the commercial.
The Chinese Restaurant - S2-E11
Continuity mistake: Elaine is talking quite loudly about to go eat at Sky Burger; the payphone is not in use. Jerry replies he does not want to, and suddenly a person is on the phone. (00:19:30)
The Chinese Restaurant - S2-E11
Continuity mistake: Elaine is by the table with the 6 people and start whispering through her teeth her proposal to cheat at the dare, The Old Man puts his hand on his wife's hand in one shot, but he's simply gesturing close to her in the next. And that woman is holding the fork in hand or not, depending from the angle. (00:07:20)
The Chinese Restaurant - S2-E11
Continuity mistake: Jerry is explaining to Elaine what to do for eggroll dare. She listens and uncrosses her arms. When he says the words "I'll give you 50 bucks" there's a cut, and Elaine's arms are again folded. It happens again right after when Jerry says she'll give the people at the table a story to tell. (00:06:10)
The Chinese Restaurant - S2-E11
Continuity mistake: When Elaine says that the hungriest should be served first, George is holding his phone book against his body, but in the immediate follow-up he's just holding it at distance. (00:05:40)
The Chinese Restaurant - S2-E11
Continuity mistake: After the 4 people bypass Jerry and Elaine, George is trying to get the attention of the man at the phone, who just turns the other way. George angrily licks his lip and leans against the corner. Cut to Jerry, and in the background George is repeating the action of leaning, in a different way from before. (00:03:50)
Continuity mistake: When the cable guy tells Jerry it'll cost him 400 bucks, he is holding the plate with the cake in his right hand, but in the following shot the left hand is holding just the fork. (00:19:10)
Continuity mistake: George walks confidently to his ex and calls her by name. Leslie's friend is taking a bite from a little celery stick, but in the following shot her hand is lowered in front of her chest. (00:16:45)
Continuity mistake: In the opening shot of The Baby Shower party, Leslie turns towards her friend and starts talking as a ponytailed woman walks in the background. The same happens in the close-up that follows. (00:12:35)
Answer: Composer Jonathan Wolff used a synthesizer, although in seasons 7-9, a real bass is used in addition. Wolff also recorded himself making hundreds of mouth noises, pops, and slaps to add to the synthesized bass licks so that each episode has a different theme. The only real "back-story" is Jerry Seinfeld was having trouble coming up with a theme song and talked to a friend who happened to know Wolff. They wanted to avoid that cheesy late 80's sit-com theme song and Wolff came up with what we enjoy now. Jonathan Wolff has also talked about this further in interviews, recently Reed Dunela interviewed him, so for a fuller account of his story; check out "The Wolff of 116th street".
Bishop73