I first encountered Clerihews years and years ago during the brief period when I had subscriptions to Punch and Private Eye, and I'm afraid I can't remember which publication introduced me to them. But The Guardian has called an informal Clerihew competition. If you're baffled as to what a Clerihew is, all is explained here, although it seems slightly inaccurate to describe GK Chesterton as `the illustrator.'
Anyway, there seems to have been a healthy response so far. My favourite is:

Catherine Deneuve
Makes many men perve;
When they see her on screen,
Their thoughts turn obscene.

I've had a totally shitty day and my brain's shrunk to the size of a gnat's testicle right now, otherwise I'd offer you a Clerihew of my own, but if anyone else wants to have a go...