Practical Joke Ideas?

[horrorstorydude]

This is awesome...you have to do it before one of the girls goes to the kitchen sink. Ok, you know that nozzle thingy at the side of the sink that if you hold down when the water is running, water will come out of that instead? Take a couple pieces of scotch tape and tape the handle to the nozzle, and aim toward where the girl would be standing, and when she turns the water on (she won't notice the tape because it should be clear) the hose/nozzle thing will spray her in the face! It's so funny!

 

[Cam]

So my group of guy friends is friends with a group of girl friends and we always play jokes back and forth, but we've been running short on jokes, and they've gotten us quite a few times more than we've gotten them. Anyone know anything we can do? We don't care if it's personally attacking their self esteem or what not. Our ideas so far have been make chocolate laxative brownies (a classic) or order an insane amount of pizza and send it to their house (another classic).
Our jokes are pretty crude and we don't want to do something not REALLY good.
Any ideas?