Specific, standalone jokes often become common enough to stand as trope. And this can happen a lot, as the jokes work best when they evolve and don't stay the same among re-tellings. Otherwise they would fall under OtherStockPhrases.

Compare StockParodies, InsultTropes, PracticalJoke.
----
!!Tropes
[[index]]
* TheAristocrats
* {{Duck}}
* EvilLawyerJoke
* AGoodNameForARockBand
* IfIHadANickel
* IfIWantedXIWouldY
* InsultToRocks
* KnockKnockJoke
* LightBulbJoke
* NoIntelligentLifeHere
* RussianReversal
* ThatsWhatSheSaid
* ThoughtAversionFailure
* TheTriple
* WhatsAHenway
* XCalledTheyWantTheirYBack
* YourMom
[[/index]]
----