Gardevoir

You were a guy out to collect some Pokémon when you came across a Gardevoir in the wild. You threw your poké ball to catch it, but you didn't weaken her enough. To your shock, she catches your ball and throws it back at you. When the ball hits you, there is a blinding flash, and when it clears, you look down to see you have been turned into Gardevoir. You look up, and see her in your body now holding another poké ball ready to catch you. (Request by user Saw slayer)