MNI (Mugglenet Interactive, a Harry Potter site) posted that they would be down for some maintience for a couple hours yesterday and I come on to find the format of the site completely changed, the templates and everything. Each subforum has a different template, one of the common rooms is christmas themed, another is covered with brad pitt, another is covered with buffy and angel, one is covered with eyeore and the last one is covered with House. Some of the forums have Lord of the Rings and others have Pirates of the Carribean on them and others have been disney themed. It was hilarious. They pulled the prank early because everyone would be expecting it to be played tomorrow so it wouldn't be a surprise to them.

Hopefully Mes can top that.

edit: Yeah I remember last year's. Everyone was so angry because they thought the site had actually been hacked into, it was funny when we found out it was just a joke. And i don't remember what my sig had been switched too, just that it been switched, lol.