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.