Legendary character that allegedly made his first appearance at Leeds festival 2004, so named for his imitation of the children’s game where you stick swords in a barrel until the pirate "pops up". This particular version however involves the guy getting inside the disgusting pit below one of the toilet blocks, then waiting for someone to be about to urinate etc, then sticking his head out of the hole and shouting "POP UP PIRATE!!" Imitate at your own risk!
Mr A: I was about to go take a leak in the bogs, but there was some guy in the pit!
Dr B: YARRRRR!! it be pop up pirate!!