(This joke has whiskers but maybe there are one or two kids who haven't heard it.)
A guy in an apartment building is practising the tuba very late at night, when someone knocks at the door. It's his neighbor in pajamas, looking pretty angry. "Say, do you know it's three o'clock in the morning and my old lady is having a fit?" --- "No, but ... hum a few bars and I'll fake it."