In Celadon City, Ash makes the big mistake of insulting perfume, which Celadon is famous for. He is thrown out. Now, he is not allowed to enter Celadon Gym, because that is the place that manufactures the perfume, and the gym leader is the owner. Slight problem. Ash actually gets help from Team Rocket, who disguise him as a girl, to get him into the gym. Team Rocket didn't do this for nothing of course; Ash had helped them escape when they were tied up for trying to steal perfume formulae.
Erika is teaching a class inside, and Ashley (^_^.) is presented as her newest student. Erika talks about how strong her bond with her Pokemon Gloom is, because it saved her life when she was small and she's had it ever since. However, Ash's disguise slips when Pikachu recognises him a little too enthusiastically. But Erika accepts Ash's challenge to battle, and they do. The battles are fairly even, but then Erika sends out Gloom. Ash is at a loss, knowing that Gloom is powerful, and the strong smell it emits is awful. Pikachu goes in to fight, but Team Rocket appear.
They strike back for revenge, doing an awful thing in causing the gym to set on fire. Bad news, since the gym is full of plants. :( Everyone escapes, but outside, Erika can't find Gloom anywhere. It's still inside! Ash doesn't want Erika to get into danger so he impulsively runs inside himself, finding Gloom but trying to hold his breath so that he doesn't breath in Gloom's bad smell. But, Gloom smells fine because it feels safe with Ash and only emits the smell when it feels threatened. The water Pokemon and humans have put out the fire after Ash and Gloom emerge safely from the gym. Erika gives Ash the Rainbowbadge for helping.