I just started a YKTTW for the trope where a sphinx asks you a riddle. To mark the occasion, I'm going to think of a cool riddle.
What has a beard but no hair,
Was brown but now is grey,
And is a piece of moldy bread?
Wait, I think I messed up somewhere. This is hard.
Okay, if I were a sphinx and I wanted to eat some poor schmoe, what would I ask?
What is the fifty-first Merseinne Prime?
I'm not sure if I'd make a really bad sphinx or a really good sphinx.