Put your balls where your mouth is
Similar to the expression "put your money where your mouth is". Can be said when calling someone's bluff. Can be said to taunt an opponent in competition or question one's bravery.
Friend 1: I'm gonna play this video game on the hardest difficulty. I mean how hard could it be?
Friend 2: No way bro. I did that it was terribly hard. If you are so brave then put your balls where your mouth is.
Friend 1: Eww!!! No way dude!!!
Friend 2: No way bro. I did that it was terribly hard. If you are so brave then put your balls where your mouth is.
Friend 1: Eww!!! No way dude!!!