There aren't a lot of ukulele jokes, strangely, but there or certainly plenty of “musician jokes.”
Often you can tell the same joke about ANY instrument.
Most are meant to be insulting to players of YOUR instrument (if you can take a joke), or else insulting to players of OTHER instruments (if you can't take a joke).
Overall, it seems that accordions get the “annoying noise” jokes; banjos get the “dumb player” jokes; guitarists get “unemployable” jokes.
And, maybe, the ukulele is actually the one truly beloved member of the instrument family, without any mean jokes of its own. I had to adapt the jokes above.
Could we really have the instrument that nobody hates?
As if to prove my theory of ukulele, I came across this illustration that seems to sum up our love of uke (make sure you have images turned on in your email reader):
Probably not anthropologically accurate, but it makes me laugh every time!