Two. One to take out the bulb and drop it, and the other to try and sell it before it crashes.
or
Two babies screaming!
or
When it's going cheep!
Did you hear the one about the crow and the telephone pole?
He wanted to make a long distance caw.
or
they always take things literally.
or
They turn from notating nuclear spins to notating unclear puns.
or
The sound of Mew-sic
or