Stopping by a small town Pokémon Center, the gang enters to see no one at the front desk. Chansey appears from around the corner, followed closely by Nurse Joy. However, Brock notices something fishy, and after closer examination, finds that that Nurse Joy is an imposter. Suddenly, Chansey begins glowing white as it transforms back to the Ditto it was. Witnessing this, our heroes discover that the true identity of the Joy imposter is none other than Ash's old friend, Duplica. Sitting down getting reacquainted, Brock finds that Duplica is in town because of the Pokémon Acting Competition, a gathering of trainers from all over competing in shows, plays, etc. Spying on the group nearby, Team Rocket remembers Duplica as "the detestable Ditto trainer" and comes up with an idea to steal her Pokémon. Back inside, Nurse Joy comes out from the ER with Duplica's other Ditto, one she nicknamed Minidit, and reports that it's at prime condition.
Outside on the playground, Brock asks Duplica why she brought Minidit to the Pokémon Center if it was already healthy. Duplica offers to demonstrate and tells Minidit to transform into Pikachu. Her Pokémon does so, and a seemingly flawless Pikachu appears. She then orders it to transform into Togepi, and another perfect transformation takes place. Baffled, Ash still can't figure out what's wrong with Minidit, so Duplica asks for a bigger Pokémon to show why. Brock sends out Onix, and Duplica commands Minidit to transform. Minidit transforms into Onix, but at a fraction of the height. Shocked, Team Rocket is convinced that they absolutely must steal that rare and valuable Ditto. Our heroes are shocked to see this as well.
As Duplica mentions that the cause of this strange behavior is still a mystery to her, Misty comments that she finds the "weirdest, wackiest, and most abnormal Pokémon ever". Duplica is hurt and devastated by the statement, so Misty tries to quickly make up by meaning it in the best possible sense. Ash tells Duplica that she's most likely to have gotten stronger the last time they met, and challenges her to a battle. As Ash chooses Totodile, Duplica tells Minidit to transform into her opponent's Pokémon.
She makes the first move, and tells Minidit to use Scary Face. Minidit runs up and puts up a frightening façade, but Totodile stands there pointing and laughing. Ash goes next, and commands Totodile to use Water Gun. Minidit stands its ground, shakes the attack off, and prepares to use Hydro Pump. However, nothing comes out, and Ash innocently tells Duplica that he's never gotten around to teaching Totodile Hydro Pump yet.
She therefore tries another attack, Tackle, and Minidit charges at Totodile and connects. Ash is about to retaliate with Bite, when a loud explosion can be heard in the distance. It turns out that the Pokémon Center's roof has been destroyed, and standing in the middle of the debris is Jessie and James dressed as Duplica and Ash. As the two distract our heroes telling them their scheme to steal all the Pokémon inside the Pokémon Center, Meowth sneaks up from behind and bags Minidit in a sack. The gang prepares to enter the building to stop Team Rocket, but Duplica finds that Minidit is missing. As she desperately looks around for her lost Pokémon,
Nurse Joy tells Ash, Misty, and Brock that Team Rocket just fled out the back door without stealing any of the Pokémon. This contradicts Team Rocket's original scheme, but Brock realizes that that must've been just a diversion while the real target, Minidit, was captured. Someplace else, James suggests that they should've stolen all of the other Pokémon while they were at the Pokémon Center, but Jessie tells them that greediness is the mistake they always make, which leads them to failure. James concurs, agreeing to settle for just one Pokémon this time. However, Meowth interrupts and comes up with a plan that'll earn dozens of more rare Pokémon: If Jessie and James pose as Pokémon traders trading a miniature-sized "Arbok", some rich Pokémon collector will eventually pass by and offer a rare Pokémon such as Dragonite to swap.
Then, after making the trade, they'll steal Minidit back and repeat the process in different towns. Jessie and James like the idea, and decide to go along with it. Ash and Duplica meet back up Misty and Brock finding no sign of Minidit anywhere. Noctowl and Ditto, who has transformed into the owl Pokémon, have no such luck either. Suddenly, Nurse Joy comes up and reports that she's just heard of a suspicious group of people in a nearby town trying to trade a miniature Arbok. Hearing this, the gang sets off to investigate.
No doubt, Team Rocket is following Meowth's plan. The trainers gathered around offer Pokémon such as Beedrill or Wooper, but no Dragonites. Jessie begins to think that the plan isn't working well, and James seconds that, suggesting that they should quit while they're ahead. Meowth tells them to be patient, when suddenly, Ash and the others find the trading post. As Misty begins to interrogate Team Rocket, who reply with indecisive answers,
James suggests that Ash should trade his Pikachu for the mini-Arbok, but he refuses. Furious, Meowth jumps in, yelling at his partners for not being able to make at least one trade, and seeing the talking Meowth, Ash immediately recognizes Team Rocket. He commands Pikachu to use Thunderbolt on the three, and Minidit's cage breaks free. Jessie gets up and sends out Arbok to fight. Wobbuffet unexpectedly comes out of its Pokéball, so Jessie decides to use it in battle as well. Duplica orders Ditto to transform into Arbok, and Minidit into Wobbuffet.
She starts by tackling Wobbuffet, but its Counter attack sends Ditto recoiling back. Jessie tells Arbok to use Poison Sting on Minidit, but much like Wobbuffet's Counter, Minidit's Counter bounces the attack right back. Meanwhile, Meowth tells James to launch a sneak attack on Pikachu. He goes for it, calling out Weezing to use Sludge. However, Duplica intervenes just in time, telling Ditto to use Wrap on Weezing.
Ash and Duplica agree to make it 3 on 3 battle with Team Rocket now. Ash has Pikachu use Thunderbolt, but Wobbuffet counterattacks and the shock is sent back at them. Duplica mentions that there's more than one way to use Counter, and tells Jessie that she has the feeling that she's afraid to attack Minidit. Jessie laughs at the idea, orders Arbok to tackle Minidit, but is sent driving into a tree when Arbok is thrown back at its trainer. James then orders Weezing to use Sludge attack, but Minidit's Mirror Coat returns the blow.
Duplica explains that Wobbuffet has two attacks: Counter and Mirror Coat. Counter is used against physical attacks such as Tackle or Bite, and Mirror Coat is for special attacks such as Thunderbolt or Sludge. James understands this, saying that Minidit only obeyed Jessie to play along until Duplica found it. Jessie is furious, and Meowth lunges forward to use Fury Swipes. Duplica's Minidit responds with Counter, and Meowth ends up with claw marks on his face. She then quickly orders her two Ditto to transform into Pikachu, and Ditto, Minidit, and Ash's Pikachu all use a Thunder attack together. Jessie, who can't remember which attack to use against Thunder, ends up indecisive as the electric shock sends Team Rocket blasting off over the horizon.
Back at the Pokémon Center, Duplica demonstrates her Minidit's capabilities to a small crowd. Ash mentions that he'd like to see a miniature Ursaring, and Minidit complies, looking just like a small teddy bear. Duplica decides that Minidit's inability to match the size of the Pokémon it transforms into is what makes it unique, and comes up with idea of specializing in making a team of Ditto who each have their own ways of transforming. She then brings up the subject of the interrupted battle she and Ash were having, and as both trainers run outside to finish the match, Duplica stops to tell Brock and Misty that it might take a while because their friend has gotten a lot smarter. Meanwhile, Jessie is still puzzled over how Duplica's pint-sized Ditto was able to outsmart her Wobbuffet. She hangs there in the tree pondering with James and Meowth, and the episode ends.