A mushroom!
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
Tooth-hurty.
or
Time is fun when you're having flies
or
Two, one to call the electrician, and one to mix the drinks.
or
They turn from notating nuclear spins to notating unclear puns.
or
What's the use, they'd still have bear feet
or
A conversation.
or
A centipede with a wooden leg.
or