Did you hear about the Spoiler: bad taste constipated mathematician? Spoiler: Really Bad Punch Line He worked it out with a pencil.
This one is safe to tell children: Why do melons have big weddings? Spoiler: Uber Groaner Because they cantaloupe...
I can do better: Do you know how to catch a polar bear? Spoiler: part I First, you cut a hole in the ice and put a bunch of frozen peas all around the hole. Spoiler: Part II-really bad-simulates dirty word Then, when the polar bear comes to take a pea, you kick him in the ice hole.
If you don't get this one, research the cardinality of a countably infinite set... Spoiler Aleph null bottles of beer on the wall, aleph null bottles of beer, take one down, pass it around, aleph null bottles of beer on the wall...
What do you get when you cross a mosquito with a mountain climber? Spoiler Nothing, you can't cross a vector and a scalar.