Noah opens up the ark and lets all of the animals out, telling them, "Go forth and multiply!"
He's closing the great door of the ark when he notices that there are two snakes sitting in a dark corner.
So he says to them, "Didn' you hear me? You can go now. Go forth and multiply!"
"We can't," said the snakes, "We're ADDERS."
Why don't skeletons date?
They don't have any BODY to go out with!
Why can't mummies keep friends?
They're too WRAPPED UP in themselves!