Revnge Help Ideas Needed!

Ok heres the deal

My friend (john) has this sister who is a year younger than all of my friends....and he went to a dance with his sister's friend and he invited another one of my friends (phil) to go with his sister...so i thought it would be funny if phil got on his sister and i told him id pay him if he did.

So back at school the monday after the dance and low and behold he got on her. I didnt believe it at first but all my friends are saying it and other people who bet him are paying phil in front of me. So i pay too. Now for over a week phil has been calling johns sister and john keeps getting madder and madder and I (altohght feeling somewhat like an ass) am loving every second of it.

Howveer...tonight i find out im the sucker. Everyone tohught it would be funny to fool me but i found out. So any suggestions on how to turn the joke around. Actually kissing his sister is def an option but she might not go along with that and my g/f might not like that either. Im open to anythnig good. Preferably something that shocks them. Thanks