well, it's only famous within my school. It was either the class of '08 or '09 who did it but they were there over night and they put chairs on staircases and string in front of building's doors, so there was only one exit, padlocked the school hall with a different lock than what they usually have, directed all the traffic (my school is next to a high way) onto our round about, so you can imagine it was hell, put a pirate flag on the flag pole, somehow directed all the teacher's cars at the junior school so they had to walk a massive hill to the high school, put a for-sale sign out in front of our school, as well as honey on garbage bins and toilets.
Then it was either the week before or day before muck up day, they gave the principle a present in assembly in front of years 7-12 which was in the sports centre, heaps of goats who shitted everywhere. The principle wasn't impressed but everyone laughed. They put the song "who let the dogs out" when they showed the rest of the goats (there was about 20-odd goats from what i remembered).
One year, i think in the 90s, they somehow put a car on the roof of our sports center as one of the muck up jokes.