Replying to NS Pranksters

Alright, so i'm on my schools ski team, and every week we go up to hood friday night for nightskiing and then stay at an Inn at the mtn and ski saturday. The girls and guys each get seperate rooms, there are maybe 8 girls and 10 guys. but anyways, last week the girls snuck into our room and dropped cell phones with their allarms set for 3:30 waking all of us up. And now we want to do something back. and thats where all you NS pranksters come in. The only thing is that we don't want to do anthing too bad and it also cant hurt anyone or any of their stuff...

Any Ideas?