Pull pranks on each other Make something weird experiment Watch a movie your friend hasn't seen Play wii Xbox or play station Draw each other Dress up Record videos of each other Do each others hair Play board games Play something together on your ipods
Truth or dare and MadLibs were always my favorites... but you could also do manicures/pedicures and makeup, watch movies/TV, play a board game/cards, look through old yearbooks, and just chat about random nonsense! there's some apps that are full of "useless tidbits of info" and "dumb laws" that are awesome for goofy conversation and some good laughs! also... seriously, you'll think I'm crazy, but way back when I was a teenager my girlfriends and I would have sleepovers and after dark we'd walk down the road to the cemetery, take random pictures, then go home to inspect them for orbs! yup, we REALLY did that, and it was SO UNBELIEVABLY FUN!