Lots of possibilities in making fun of the formality of classical music. Take the Marx Brothers, for example:
But my favorite has always been Victor Borge:
There is a little known piece by John Dowland "for two to play on one lute" that is just as funny. Not for the music itself, but the contortions involved in the performance. Just as the audience settles down to enjoy the music, the players switch parts and more hilarity ensues:
Alas, most performers don't let themselves enjoy the comic aspects of the piece! But I have performed this in public and it can be nearly as funny as the Borge performance of Liszt. And this was written this way! Good set-up line: "hands off my G-string!" How about some more Victor Borge?
It's the incongruity that makes for the humor: famous virtuoso pianist can't get it right, but every backstage blue-collar worker can just toss it off, even wearing gloves. Lots more Borge on YouTube for you to watch.
But we also have musical humor. There are only a few composers really good at musical humor and probably the best is Haydn. Here is a minuet that is so rhythmically twisted that the first rehearsal is likely to be pretty hilarious for the players:
Then there is his famous quartet from op 33 nicknamed "The Joke" because the last movement has multiple false endings, each tempting members of the audience to burst into applause before the piece is actually over:
That almost worked! I think audiences nowadays are so cowed by the tsk-tksers that they live in fear of clapping in the wrong place--even when the composer tempts them. Another composer with a sense of humor--though rather dark at times--was Shostakovich. Here is his setting of "Tea for Two" which he re-named "Tahiti Trot" and orchestrated for his ballet The Golden Age:
Here is a polka from that same ballet, arranged by Shostakovich for string quartet:
Another humorist in music is Beethoven, but I'll save that for another post as it takes a bit more context. But this post was inspired by a post on Norman Lebrecht's blog about a recently discovered letter from Beethoven. The letter was written to a composer named Stockhausen--alas, not Karlheinz, but a Franz Anton Stockhausen, living in Paris. Norman comments, "As usual, Beethoven complains about his health and living conditions. He does not, sadly, offer analysis or criticism of Gruppen." That sounds like good material for another post!