Involves no penile or vaginal contact. It requires you getting naked. Okay, I lied, it requires penile contact. You do a leapfrog, but you're both naked, and the guy leapfrogs over the girl, and the penis drags all along the backside of the girl.

when you're hungover as shit after a spending a night drunk as a skunk

A sexual maneuver that involves at least one man. Works just like leap frog, except the (or a) man drags his genitals up and along the back of his partner.

The frog smile is a sexual act performed by a man and a woman. Both participants must be naked with the woman standing in front of the man. The man then leapfrogs over the woman, dragging his penis and balls across her back and head.

a sexual maneuver where a naked man leapfrogs over a naked woman causing his penis to drag across her back.

A sexual act in which a naked man drags his flaccid penis across a naked woman's back ,in a leapfrog motion, to get his penis erect.

A sexual act in which both partners play a game of leapfrog whilst naked.

(Originates from part 25 of the Game Grumps playthrough of Sonic Adventure DX)