!!This show is the TropeNamer for:

* KavorkaMan
* NotThatTheresAnythingWrongWithThat
* SeinfeldianConversation
* SeinfeldIsUnfunny [[invoked]]
* Former trope namer for Sein Language (Now TheCatchPhraseCatchesOn) [[invoked]] and The European Carry-All (Now LessEmbarrassingTerm)
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* FakeBrit: Norman Brenner's character in "The Wig Master".
** Subverted. Brenner is actually British.
* HeyItsThatVoice: J. Peterman's actor can unmistakably be heard as the voiceover in current Coors Light commercials.
* OldShame: Regis Philbin loves the series, so he was disappointed that when he guest starred, he was given a line that he didn't think was funny (three variants of "This guy's bonkos!"). The producers insisted it would be hilarious, but his lines didn't get very many laughs with the studio audience. To this day, Regis dreads watching that episode for that reason.
* TheOtherDarrin: Phil Bruns originally played Morty Seinfeld, but after his initial appearance, he was played by Barney Martin.
** Larry David originally played Newman in "The Revenge" (he provided his off-screen voice), but his first on-screen appearance was by Wayne Knight. In syndication, Knight dubbed over David's voice in "The Revenge" to provide some continuity. However, both versions of the episode are available on the DVD set.
** John Randolph originally played Frank Costanza in "The Handicap Spot". Later, Jerry Stiller replaced him in "The Puffy Shirt". For syndication, John Randolph's scenes in "The Handicap Spot" were re-shot with Jerry Stiller in his place, to provide continuity. However, as with the previous example, both versions are available on DVD.
** Lloyd Braun was initially played by Peter Keleghan, and later played by Matt [=McCoy=] in "The Gum" and "The Serenity Now".
* TheOtherMarty: See the above trope for details.
* RoleAssociation: Hey, it's [[{{Series/Friends}} Monica, Janice, Susan]], [[{{Series/Frasier}} Daphne]], [[{{Series/That70sShow}} Kitty]], [[{{Series/EverybodyLovesRaymond}} Robert]], and even [[{{Series/House}} a youthful Dr. Cuddy!]]
** [[{{Series/DesperateHousewives}} Another Susan, too, and Bree]]. And [[{{Series/Scrubs}} Jordan]], [[{{Series/Scrubs}} the Janitor]] (who is now a nameless police officer) as well as [[{{Series/Scrubs}} Ted]]. [[{{Series/TheSarahSilvermanProgram}} Sarah]] even shows up too.
** [[{{Film/ReservoirDogs}} Joe Cabot]] played Elaine's father, while '''[[{{Film/Saw}} JIGSAW]]''' played the owner of a used records store.
** [[{{Series/Lost}} Jin-Soo Kwon]] was a doctor in one episode.
** [[Film/{{Beetlejuice}} Otho]] is Jerry's landlord and [[{{Series/BreakingBad}} Walter White]] is his dentist!
** Creator/PatrickWarburton, ake non-animated [[{{WesternAnimation/FamilyGuy}} Joe]].
*** Don't forget he's also the non-animated [[{{WesternAnimation/TheEmperorsNewSchool}} Kronk]]
** Lest we forget [[{{Series/WhiteCollar}} Agent Peter Burke]] as Bizarro Jerry.
** Or that Jerry once dated [[{{Series/LoisAndClark}} Lois Lane]].
** Jerry dumped [[{{Series/TrueBlood}} Pam]] because of her hands.
** "Eric" the clown was a [[{{Film/Swingers}} Swinger]].
** Don't forget, the Postmaster General has [[MemeticMutation DAHH'BEETUS.]]
** George once dated [[{{Series/StarTrekTheNextGeneration}} Ensign Ro]]
** The stationery store owner from "The Big Salad" is none other than [[{{Series/WillAndGrace}} Larry]]
** [[{{Film/AmericanPie}} Stifler's Mom]]/[[{{Series/TwoBrokeGirls}} Sophie]] is the masseuse Jerry dates who won't massage him.
** After losing the case in the finale, Jackie Childs moved to [[{{Series/Smallville}} Metropolis]] and became the [[MartianManhunter John Jones]].
* WhatCouldHaveBeen: Larry Miller was originally cast as George, but it was decided that, just to make George a little bit more pathetic, he needed to be short. Miller eventually appeared as a [[DiabolicalMastermind doorman]] that could give [[{{Series/Scrubs}} The Janitor]] a run for his money.
** The project began as just a 90 minute special about a day in Jerry's life, and how it inspires his stand-up material that night. Jerry and Larry David couldn't quite stretch the script to fill the 90 minutes, so they reduced in down to half an hour as a series pilot. As Jerry would later say, "We couldn't make 90 minutes, so we made 90 hours."
** Elaine's father was intended to be a recurring character, but then they hired the notoriously ill-tempered and intimidating Laurence Tierney to play him, and after filming the episode, no one wanted to work with him again. Among other things, [[EnforcedMethodActing Jason Alexander and Jerry were genuinely intimidated]], and Tierney was seen stealing knives from the apartment set.
** The waitress in the pilot was meant to be the show's female lead. The [[ExecutiveMeddling producers]] thought the show needed a female lead ([[FridgeLogic although if the show already had one, it's a wonder why they felt a new character was needed]]), so Elaine was written into the show.