Programming Jokes

Post some of your good programming jokes here!
A good one I know is:
"My other car is a cdr" as in car and cdr from LISP

Also,
Why do programmers always confuse christmas and halloween?
Because oct[31] = dec[25]

I like this joke:

A constant and e^x are walking down the street when they
see a differential operator approaching. 

The constant panics and runs away, naturally, but e^x says
"Ha, watch this, coward, I'll go shake hands with him."

When e^x introduces himself, the differential operator says
"Hi, I'm d/dy."