I think the only mathematics joke that I've come up with myself is "Almost-all numbers are normal" - a self-evidently true statement, which nevertheless means s

I think the only mathematics joke that I've come up with myself is "Almost-all numbers are normal" - a self-evidently true statement, which nevertheless means something wildly different than what a layman might believe - indeed, the numbers that a non-mathematician might be most likely to imagine or name are in fact not normal!