When you step on someone's flip flops
Mark was looking like a douchebag with his flip flops, so I gave him a foot wedgie
Derived from the word wedgie, meaning an uncomfortable tightening of underpants between the buttocks, a foot wedgie is related to the foot.
A foot wedgie can only be achieved if the victim is wearing flip flops. Like a standard wedgie, a foot wedgie can be caused through accident or prank.
In a prank scenario, the victim will be in motion, while the antagonizer walks behind them. The antagonizer will then step on the back of the flip-flop causing the victim's foot to continue in motion while the shoe is stationary, thus creating a painful sensation as the strap between the victims toes is yanked back.
It can also be caused by the victims own carelessness if the front of the flip-flop is caught under something while in motion, or rams against something low to the ground the victim didn't notice, while in motion.
To bug his sister, Johnny walked behind her and stepped on the heal of her flip flop to give her a foot wedgie.