That's basically what it is. Try to think of a story of one of the girls in pokemon having to pee and something is keeping her from doing it.

Both needing to relieve their bowels, May and Jessie head towards the only toilet. After some argueing on who goes first they decide to settle it with a battle.

 Its not easy to command a pokemon in battle when you gotta poop. But Jessie decides to play dirty and starts comanding her pokemon to stimulate May, such as punch her in the stomach or tickling her. But may has a few tricks up her sleeve.

 choose who you want to win.