Here's my favorite sucky math joke. Q. What's special about the number 17? A. It's the smallest prime, the sum of whose digits is 8!
Ha, ha, I never get tired of that joke.
How does a differential topologist visualize 96-dimensional smooth manifolds? He first visualizes N-dimensional smooth manifolds where N is greater than or equal to some sufficiently large number. Next, he does a calculation on the side to confirm that 96 is sufficiently large, for the purposes of the present discussion. Then he substitutes 96 for N.
Theorem. A cat has nine tails. Proof. No cat has eight tails. Since one cat has one more tail than no cat, it must have nine tails.
Q. What is purple and commutative?
A. An abelian grape...
Q. What is glazed and filled with jelly?
A. A topologist's coffee cup.
A statistician is a person who thinks he's average because he has one testicle and one ovary.
What is the difference between a Psychotic, a Neurotic and a mathematician? A Psychotic believes that 2+2=5. A Neurotic knows that 2+2=4, but it kills him. A mathematician doesn't care what 2+2 is, so long as 2 and + are well-defined and the axioms determine the value of the operation.
How much does Technorati suck? Let S be the set of all ways that Technorati sucks. If I remove any one element of S, the remaining set can be placed in one-to-one correspondence with the original set S. That's how much Technorati sucks.