www.prankdial.com
and
www.prankdial.com/prankevil.php
Its basically a site that allows you to prank friends with certain pre-recorded conversations, and listen to them later!
The second link is the best though, it lets you hook up two of your friends (or strangers), so it looks like they both called eachother! Check out the one I did on some coworkers, hilarious!
http://www.prankdial.com/hearprank_l5448484q213y2.php