A Rupert is a dude that could never become a John. The arch nemesis of a John (Johnanation). A Rupert is typically one of those guys you see who thinks he's a bad-ass dude but he's really just an asshole and nobody likes him. Ruperts usually come from Broseville and have lots of their dad's money.
Chandler: " Hey, John, hows it going?"
Travis: "There's a Rupert at the bar, being a dick"