The late Matt McGinn also used to drive his accompanists potty by starting in one key, stopping mid song to make some remark, and then going back to the song in whatever key he fancied. Talk about rapidly sliding capos!
The deliberate key change: usually a whole tone up, is the hallmark of every Eurovision Song contest entry, so much so, that if a folkie does it, maybe in a repeat of final chorus, its' "Aha, the Eurovision key-change!".
And that's a bit of thread drift, I fear.