The moment when someone tries to do something they otherwise wouldn't do under the banner of YOLO, and fails miserably and the end result is hysterically funny to the person watching.
Jock 1: Hey Schneebly, if you can get with that chick from the cheerleading club, i'll join the chess club and tell everyone you're hung with a massive bear cock, shlonger than a horse
Nerd 1: One would hypothesise that the chances of that happening are little to zero. but oh well as they do say, 'You Only Live Once'
*Schneebly triumphantly fails and bears the embarrassment of a horrendous wet patch around the genitalia for the rest of the day. the excitement of it all also leaves a nasty amount of fresh knob cheese strewn all over his new boxers.
Jock 1: Dude! YOLOL