Gymbaliar! (なぞのジムのグレッグル！ Croagunk and the Mysterious Gym! ) is the 8th episode of Pokémon: Diamond and Pearl.
Still en route to Jubilife City, Ash and co. meet a girl named Minnie who tells the gang about a Gym called the Powerzone Gym. As usual Ash wants in on the Gym Battles so he, Dawn, Brock and Minnie check it out. What kind of Gym is this, and is it authorized by the Sinnoh League?
Jessie's Dustox battles a Marowak. The former uses Stun Spore, but gets deflected. Dustox dodges Marowak's Bonemerang, but the bone returns and hits her. Marowak defeats Dustox with Bone Club. The challenger, Jeffrey, wins and gets a badge, making James sad. Meowth goes to the grocery and buys some drinks. He spots a Croagunk and makes him nervous. Meowth ignores it and goes away, but he realizes its following him. He runs away and comes back to Jessie and James. The Croagunk followed him to there. Meowth translates that Croagunk thinks they are boring. James goes to modify its face to make it look happier, but gets hit by a Poison Jab. The Croagunk is still bored, but Jessie has an idea.
Meanwhile, the heroes continue to go to Jubilife City and see that an Scizor approached them. A trainer comes and Brock flirts with her. The woman says they are on their way to a new Gym named Powerzone Gym. The woman's name is Minnie and the heroes introduce themselves. Later, they approach it. Inside, Croagunk battles a Sandslash. Sandslash uses Sand Attack, but Croagunk dodges and defeats it with Poison Jab. Since Sandslash got defeated, Team Rocket take the trainer's Poké Ball to improve the Pokémon. Team Rocket see the heroes and think about this through. Jessie picks Minnie first to fight.
James tells it is a 1-on-1 battle. Dawn wants to see the badge. James and Meowth are surprised, as they have no other "badges". James presents the badges - bottle caps. The heroes are not much impressed, though James yells at them for that thought. Brock shouts for Minnie to win, but gets pounded by Jessie. Jessie calls for the referee James, who tells Jessie wins this. Croagunk starts with Poison Sting, but Scizor evades and uses Quick Attack, then Slashes Croagunk. Scizor defeats Croagunk with a Metal Claw. James goes to call Minnie a winner, but Croagunk stands up. The latter uses Brick Break and Scizor misses, but Croagunk repeats its attack and hits Scizor. The latter gets defeated by the former's Poison Jab. Team Rocket tells Minnie they will "train" it. Still, it is Ash's turn, but Jessie tells it is time for lunch, so they go out, while Jessie makes her next plan.
Ash sends Aipom. Croagunk uses Brick Break, but misses and Aipom retaliates with Swift, then uses Focus Punch, hitting Croagunk, though it counter-attacks with Poison Jab. Aipom is stun by the attack and Croagunk attacks once more. Aipom uses Double Team and follows with Swift to attack. Aipom defeats Croagunk with Focus Punch. James tells Ash is the winner, but Meowth says that it is not over - the winner is only one who defeats Pokémon twice in a row. Jessie sends Dustox and Ash about to send his Turtwig, but Jessie stops him and the rules tell the challenger's Pokémon is the Gym Leader's choice and states that Pikachu must battle. Ash has no choice but to send him. Suddenly, before something could happen, Pikachu is taken by a mecha hand, the Gym crashes and Team Rocket take their disguises off in their balloon. The heroes go after them, leaving the Croagunk alone. Ash sends Starly, who pops the balloon using Quick Attack after striking a mark the first two tries. Pikachu is freed from the net. Jessie sends Dustox to battle, but she, along with Team Rocket, gets blasted off by Pikachu's Thunderbolt.
Minnie gets her Scizor back and promises to give the Poké Balls to their trainers, as she does not want to go on a journey yet. They soon see Croagunk, who didn't blast off with Team Rocket. Croagunk wants to go with Brock, who takes out a Poké Ball out and catches Croagunk. Minnie says goodbye and Brock flirts with her again. Croagunk comes out and uses Poison Jab on Brock and pulls him away.
- This episode was the first to have the return of an old running gag, with a new twist: Whenever Brock flirts with a pretty girl, Croagunk would Poison Jab him and then drag him away.
- Meowth breaks the fourth wall, saying "there's three minutes left" when there is three minutes left in the episode (when watched without commercials).
- This is the first episode to have sparkles whenever a Pokémon exit out of a Poké Ball.
- Jessie's Dustox used Stun Spore, despite the attack is not available for it in the games.
- When Jessie ordered Croagunk to use Poison Sting during Minnie's battle, it used Brick Break.
- When Croagunk used Poison Jab on Minnie's Scizor, it injures it when originally, Poison type moves doesn't affect Steel types like Scizor.