Ash, Misty, and Brock stop at a telephone booth so that Ash can call home. He leaves a message telling his mom that he's coming back to Pallet. They set off towards Ash's hometown so that he can ask Professor Oak about the Pokémon League. Ash starts to run, but slams into an invisible wall. Brock knocks on it, and Ash notices a Pokémon climbing up it. He checks his Pokédex and it tells him that the Pokémon is a rare Mr. Mime. He prepares to catch him, but a woman approaches from behind and asks him to let her. Ash starts to protest, but Brock (who now has a crush on this woman) stops him. Mr. Mime jumps down and starts to run off. The woman throws a Pokéball at him, but it bounces off of the invisible wall. Brock apologizes and tells her that he'll help her solve whatever the problem is that she seems to have.
She leads them to a circus tent, and introduces herself as Stella, the ringmaster. A few other circus workers ask her if she got another Mr. Mime, but she sadly says no. She then takes Ash and his friends over to a trailer. Inside is a very lazy looking Mr. Mime lying on a couch. She tells them that she had trained Mr. Mime too hard and now it won't listen to her. She says that she wanted to get another Mr. Mime to provide some competition so that he will be jealous and perform again. Brock tells Stella that he can get her another Mr. Mime, and Ash asks him how he's going to manage that. Brock replies that he can make one, and when Ash asks how, he grabs him, telling him that he can help.
Meanwhile, deep in the forest, Jessie and James stop at a Team Rocket complex. They call their Boss and apologize for destroying his gym. He yells at them for wasting his time, and they run off. He turns to the Pokémon in front of him (the Pokémon Gary saw) and tells him that no one will ever find a Pokémon as rare as him. Team Rocket talk to each other in their balloon, and Meowth wonders where they'll be able to find a rare Pokémon. An advertisement for the circus blows into his face, and Jessie looks at the picture of Mr. Mime on it.
Back at the circus complex, Stella and Misty look at what Brock has done. In front of them stands Ash dressed as a Mr. Mime. He asks why he has to wear the costume and Brock says that he is too tall. Misty's excuse is that she can't hide a face like hers. Stella and her workers beg Ash to do it, and Brock tells him that Stella will teach him everything he'll need to do. Finally, Ash agrees, and Stella starts in with the training, cracking a whip and telling him to start pantomiming. Ash tries his hardest, and Stella continues cracking her whip. Brock and Misty go back to the trailer, but Mr. Mime doesn't appear to care about this "competition."
The next day is the day of the show, and Stella leads the show. Ash notices his mother in the crowd and shouts out, only to be reminded by Stella to keep quiet. Suddenly, all the lights go out except for two spotlights near the trapezes. It's Team Rocket, and they say their motto as they swing through the air. They fire a net at Ash in the Mr. Mime costume, catching him. They reel him up into the balloon and take off. Ash's mom approaches Misty and Brock and asks them if it was really Ash that Team Rocket stole. They sadly say yes. Mrs. Ketchum, however, isn't too worried, for she says that once Team Rocket discover that they didn't steal a Pokémon, they'll let Ash go. Brock and Misty happily agree, and Mrs. Ketchum invites them over to the house for lunch.
Elsewhere, Team Rocket eats lunch in a cabin while Ash, still in the costume, works at untying himself. He does so, and takes off the head, scaring Team Rocket. He tells them he's not a Mr. Mime, and walks out the door. Team Rocket, furious, dash out the door to stop him, but Ash has taken their balloon and is going home.
Back at Ash's house, Brock, Misty, and Stella thank Mrs. Ketchum for lunch. They walk off, and she goes back inside. She sits down and starts to worry about her son, when a real Mr. Mime knocks on the door. She thinks that this is Ash and lets him inside, giving him some lunch. He quickly starts to eat. Minutes later, the balloon lands in front of the house, and Ash climbs out and goes inside. His mom looks out from the kitchen to see both the real Mr. Mime and Ash in the costume. She gets confused and Ash pulls off the head of his costume. She smiles, saying that she didn't think the Mr. Mime was him, as he ate so nicely. Ash asks Mr. Mime to help him out, but it takes some convincing from his mom before he agrees.
Meanwhile, Team Rocket approaches the circus in a tank, and prepares to catch all the Pokémon there. They fire a missile, and a net falls over a Dodrio. They fire a few more, catching more of the Pokémon in nets. The circus workers free them, and herd them into trucks. They start to leave, but are stopped by another net. James looks around for Mr. Mime, and spot him running with Stella. Mr. Mime is slightly out of shape, and is getting tired. Stella tells him to climb onto her back, and she starts running with him. Team Rocket aims at them and prepare to fire, when Ash jumps into the way. Stella turns around, and Brock and the rest arrive onto the scene. Team Rocket yells at Ash to get out of the way, but he has Pikachu use a Thunderbolt on the tank. It has not effect, however, for the tank is made of rubber. Team Rocket starts up again and start driving towards them. Ash sends out Charizard in the hopes that he'll melt the tank, but he still won't obey. Ash returns the fire Pokémon, and dives out of the way of the tank.
Ash's mom asks Mr. Mime to do something, and he jumps into the path of the tank. Team Rocket stops, and fires a missile. Mr. Mime quickly creates a barrier, and the missile is deflected. Mr. Mime creates a few more barriers, and Team Rocket tries to ram it down. They are unsuccessful, however, and just sit there spinning their wheels. Stella raves over the performance, and her Mr. Mime starts to get jealous. Team Rocket turns around, and head towards where Brock, Misty, and Stella stand. Stella's Mr. Mime, however, creates another wall, and the tank crashes into it. The other Mr. Mime approaches, and they both start to try to show each other up by creating more and more wall tiles until the tank is completely surrounded.
Ash and his mom rush up to Mr. Mime (Mimie, as Mrs. Ketchum now calls him) and he gives her a hug. Stella walks up to her Mr. Mime, and apologizes for being so harsh. Mr. Mime agrees to perform in the circus again, and they hug each other as well. Inside the huge box, Team Rocket tries to blast their way out of the cage with several missiles, but only manage to blow themselves up and into the air.
That evening, back at Ash's house, Mimie has become part of the family, and is helping cook dinner. Misty tells Ash that at least Mimie has manners and helps out around the house. Ash protests, but then sighs. Mr. Mime is going to be around for a while.