Guy is dancing awkwardly at a club with hot girl. The girl is starting to lose interest in him. In a desperation move, he does a mustache dance - twitching his upper lip to the music to make it look like his mustache is dancing. The girl loves it, she moves in closer. HANDLED IT.

Ending could be girl grinding against guy and his mustache would shoot up suggestively.

The mustache dancing could be done by the actor. Or we could do stop motion. Or a digital effect in post for crazier movement.