You wanna know how I know your gay?
used to make someone aware that they are about to be told why they are gay. Used several times in a popular movie starring Steve Carrell called 40 Year Old Virgin
Bob: You wanna know how I know your gay?
Callum: How?
Bob: Because you got a tent when playing rugby in sports lessons . . .
Callum: How?
Bob: Because you got a tent when playing rugby in sports lessons . . .