Talking of ones mind drifting during performances reminds me of an incident. I was gigging this pub - somewhere in the depth of Warwickshire, waiting for my turn to go on, and my concentration started to wander and i was checking out the room's decor. there were plates hung on the wall.

When I got 'onstage', the first thing I said was, look those plates with red indian prints on that they sell in the Radio times! somebody actually buys that shit!

The Landlady was convulsed with laughing and the Landlord shouted, That was MY choice, smartarse!