This always comes to mind when someone mentions pranks. I don't know where it originates from, but has traveled across the internet wide. My guess is 4chan.

Fair warning: The following text can be offensive to some, so if you don't like your humor raunchy with an extra helping of gravy, then don't look at the remainder of my post.

<TheVirus> So I had a girlfriend for all of 9 months. She dropped by one afternoon when I was sick with a pan of brownies and a video tape with the simpsons on it (my favorite show). so I start eating the brownies and turn on the tape. midway through it, it cuts to her sucking off some dude. he nuts in her mouth, she looks at the camera, and says "you're dumped. enjoy the brownies" - and spits the mouthful of cum into a bowl of brownie mix.

<alexandr-> you didn't keep eating the brownies did you?

<TheVirus> sure did

<TheVirus> i was hungry

@Onyxmeth

Actually this particular story is probably bogus. The writer is playing on very public fear that we may be the victim of food tampering, and giving it the familiar twist present in this all to common urban legend.

http://www.snopes.com/racial/crime/toothbrush.asp

It's on the internet, so it's as real as any other story presented on any forum. All of this could be bogus, but this is mainly a place to get out some awesome prank ideas. I know about the urban legend too, but that's more the reason someone would try to imitate it. I would like to think it was true, just because it's one of the more fucked up pranks I've ever heard.