Alex Ross' blog The Rest Is Noise linked to The Juilliard Manuscript Collection.
I spent only five minutes looking at musical manuscripts. It's a very cool and efficient website.
During that 5 minutes I found this mirthful little example from the hand of a famous departed composer. I provide it anonymously because even these 4 little notes are probably an egregious copyright violation.
Since at least one of my three readers is not (much of) a musician, for a mere five dollars I'd be happy to send a free explanation of what is wrong with this particular mixed meter.
Mis-Noted Tags: music notation. . . Juilliard Manuscript Collection. . . musical errors
P.S. Besides telling Viola Jokes, musicians know a few Dancer Jokes. One that I tell is "How does a Dancer count to seven?". Sorry, but the punchline can't be typed, it must be counted out loud.