[pzhon]

There are quite a few mathematician-physicist-engineer types of jokes, not all of which involve a spherical cow. My favorite is not the nerdiest, but I'll give it anyway:

A physicist, biologist, and mathematician watch two people enter an elevator. Some time later, three people get out.

Physicist: That's just experimental error.
Biologist: No, that was reproduction.
Mathematician: If one person now enters the elevator, it will be empty.

It sounds like a mathematician came up with the punchline since it is based on how mathematicians think, rather than how mathematicians are perceived by others.