You just reminded me ... Before I really got into IT in my career I was at a job that still had a messenger for the internal staff. I set my status message in it to "Raising Skinny Elephants Is Utterly Boring."
I got chastised and made to change it, because the message might offend ... Skinny elephants, I guess? I never got clarification on that.
(The manager had no clue what it meant.)

Couldn't say - I've never had the chance to use it. In fact, I'm not sure I ever had the SysRq key on a keyboard I've used.
I have had a Pause/Break key and used to think they were the same thing, but now I'm not so sure.