Sometimes it can be fun to change the usual tempo to a song or tune. At out regular session we very occasionally play 'Slow the Plough'.
ie starting 'peed the Plough' very very slowly & then build it up gently & then on the call do it one last time with a furious race to the end. It's only an occasional bit of fun though.
Another thing that sometimes happens is when a punter in the pub keeps on shouting "why don't you play an Irish tune" we just play something (probably not Irish because we don't know all that many Irish tunes) at breakneck speed & he is happy and none the wiser. The general public tend to equate any up tempo tunes with Iirishness!
Cheers
Les