Some viola jokes disparage the instrument itself. (The difference between a viola and a trampoline: You take your shoes off to jump on a trampoline.) More often, they disparage the player. (What do violists use for birth control? Their personalities.)
Violists are depicted as inherently nonmusical. (Why are violists’ fingers like lightning? They never strike in the same place twice.) Reverse viola jokes provide violists’ revenge. (Why are viola jokes so short? So violinists can remember them.)
Some viola jokes are narratives. (When the orchestra manager broke up a fight between a violist and an oboist the latter said that the violist had knocked his reeds all over the floor. “He had it coming,” cried the violist, “he retuned one of my strings and now he won’t tell me which one!”)
This according to “No laughing matter: The viola joke cycle as musicians’ folklore” by Carl Rahkonen (Western folklore LIX/1 [winter 2000] pp. 49–63).
Above, a viola joke by Charles Schulz; below, a particularly elaborate viola joke.