A troll, a hag and a leprechaun who all go into bar

'It is my very great pleasure to inform you that the Triwizard Tournament will be taking place at Hogwarts this year.'
'You're JOKING!' said Fred Weasley loudly.
The tension that had filled the Hall ever since Moody's arrival suddenly broke.
Nearly everyone laughed, and Dumbledore chuckled appreciatively.
'I am not joking, Mr Weasley,' he said, 'though, now you mention it, I did hear an excellent one over the summer about a troll, a hag and a leprechaun who all go into a bar -'
Professor McGonagall cleared her throat loudly.
'Er - but maybe this is not the time... no...' said Dumbledore.

THE TRIWIZARD TOURNAMENT - Pg 158