At a party many years ago in a large house with three seperate toilets, we found that the girls seemed to only be using the downstairs one as it was out of the way, and few people knew of it, so they could come and go without being seen by most partygoers. Anyway, it was our party and we had bought masses of drink, which had just about bankupted us, but all the girls just kept to themselves laughing at whatever the boys did, so we decided to wreak a terrible revenge. We found a blue light bulb from somebody's bedroom (this was in the early 80's) and swapped that for the one in the toilet while no one was in there. This made it rather dark. Not too dark, but in keeping with the party in many ways. We then decided to put cling film across the toilet bowl and leave the seat down, so that the next girl to pee in there would get it all over the place. We positioned ourselves as close to the toilet as we could, and you should have heard the screams that eminated from there. I cant remember the state of the girl who was in there, but she stormed out mouthing obscenities I had not heard even from my mates.