There's a new Gym in Sinnoh, and Team Rocket is in charge! With Jessie as Princess Powerzone, the Gym Leader, and James as a crooked referee, there should be no way they can lose to their latest challenger—yet somehow they do. After the battle, Meowth goes out to get snacks and comes back home with an ominous Croagunk on its tail. Croagunk isn't impressed by Team Rocket, but they're impressed by Croagunk's Poison Jab move, so they recruit the Pokémon to help them out.
Elsewhere, our heroes encounter a Scizor and its Trainer, Minnie. Minnie is headed for the Powerzone Gym because she's heard that losing Pokémon can stay at the Gym to receive extra training. Minnie thinks it would be good for her Scizor, and Ash and his friends can't resist the chance to tag along. Ash wants to battle first, but Jessie wisely pretends not to hear him and chooses to battle Minnie instead.
James' creative refereeing gives Croagunk the victory over Minnie's Scizor, so Minnie lends Scizor to the Gym for training. Ash and Aipom are up next, but when Aipom wins, Jessie declares that Ash must battle her again—with Pikachu! That's the cue for Team Rocket to unmask themselves and their Pokémon-grabbing plan... which turns out to be no match for our heroes. Another Team Rocket scheme, foiled!
This still leaves the problem of all the Trainers who left their Pokémon with the Powerzone Gym. Minnie volunteers to watch over the Pokémon until their Trainers return, but Croagunk doesn't have a Trainer. So when Brock asks Croagunk if it wants to join him, it accepts. It's an easy catch, but it won't be that easy for Brock now that Croagunk is there to use Poison Jab every time he tries to swoon over a pretty girl!