Methods known to have been used are:
1) The Brain: squishing your testicles together so that they look like a brain.
2) The Goat: tucking your penis and testicles between your legs while mooning the person.
3) The Wristwatch: Wrapping your cock and balls around your wrist.
4) The Bat Wing: Sheltering you're penis while stretching your sack just enough so that it looks like a bat wing.
Unexpecting person: What?
Prankster: THE BRAIN!! *shows cock*
UP: *looks unexpectredly* AAHHHHHHHHHHHHH!!
Prankster: HA FAGGOT!! *kicks UP in the ass.*
And that's how you play the Fag Game!