i'm going to do you all a favor and share with you the best prank ever. frankly it's my signature and i'm kind of shocked i'm sharing it with you all but it's too good to keep to myself.
step one: take your friends cellphone while they aren't looking
step two: look up your name in their cellphone address book and edit your name as it is currently listed to someone of importance to your friend. i.e. an ex boyfriend/girlfriend, spouse, mother, father, sister, brother, boss or current crush
step three: put your friends cellphone back just as you found it
step four: from your cellphone text something fabulously naughty. you see, as you are texting from your phone your unassuming friend will think it is coming from someone else.
step five: continue the charade, f@ck with them, pull their leg, play along, but do it from a distance, your phone can't immediately buzz the second they hit send.
step six: eventually you will have to fess up to your friend and let them know that it was you all along. but damn it's fun to see them squirm.
but remember kids, this is a hilarious and great prank but don't cross the line and be malicious - it's all for fun.