'The League' Star Jason Mantzoukas -- I Don't REALLY Play Fantasy Football

One of the stars of "The League" -- a show about fantasy football -- DOESN'T REALLY PLAY FANTASY FOOTBALL!! Kinda weird, right??

Jason Mantzoukas -- who plays insane cousin Rafi (aka the guy on the show who sometimes orgasms when he poops) ... was at an Xbox One party in L.A. recently when he dropped the bombshell.

WTF??? It's kinda like finding out Bryan Cranston doesn't really know how to cook meth.