Duplica's Ditto first appeared in Ditto's Mysterious Mansion, in the form of a Pikachu and playing with Ash's. However, its face was different to other Pikachu, leading the others to believe that it was a new species. Excited, Ash tried to capture it, but Duplica revealed herself and that her Pokémon was in fact a Ditto. Ash doubted Ditto's ability in battle, but accepted Duplica's challenge. Ditto easily defeated Ash's Bulbasaur using Vine Whip.
Duplica revealed that unlike most Ditto, it could not change its face when it transformed into other Pokémon, which was holding them back from becoming famous, as the Ditto face disappoints her audience. Team Rocket promptly decided to steal Ditto, coax it into the shape of a Dratini and present it to Giovanni as a gift. With help from Weezing, they succeeded in stealing Ditto. However, Ditto was incapable to meet their demands, transforming into a mutation between a man and a Dratini, then into a book instead of the Dratini pictured. When forced to turn into a Meowth, Ditto was so intimidated that it rubs its face and transforms correctly.
Ash, Duplica and the others then turned up at Team Rocket's hiding place, where they were confronted by identical Meowth. Team Rocket tried to pass off Meowth as Ditto whilst they escaped, but Duplica could tell the difference despite the transformation. Duplica threw Meowth at Team Rocket, causing Ditto to fall free. It transformed into a cannon and blasted Pikachu at the balloon, who caused Team Rocket to blast off. Now that Ditto could transform perfectly, Duplica reopened her theater for performances.
Ditto reappeared in Imitation Confrontation, disguised as a Chansey. Once Brock caught Duplica out for impersonating Nurse Joy, Duplica revealed herself and told the group that they were there for an acting competition. Once Duplica's new Ditto, Mini-Dit, was stolen, Ditto transformed into Noctowl to help search, but to no avail. When the group did discover Team Rocket, Ditto transformed into Arbok and used Wrap to keep Weezing out of the battle. It then transformed back into Pikachu and teamed up with Ash's Pikachu and Mini-Dit in the form of Pikachu to send Team Rocket blasting off with Thunder.
Personality and characteristics
Ditto is the master of transforming into many other species, including items as shown when Ditto was in Team Rocket's custody during its first appearance. At first, when Ditto transformed, the transformed being retained Ditto's face. This happened until Meowth wiped it off and retained the face of the Pokémon it transformed into. Ditto is also a powerful battler, being able to defeat Bulbasaur with ease.
Duplica's Ditto appears in Pokémon Zany Cards, as a card in Special Seven mode. Playing this card changes the suit of the card to the player's choice.
When Ditto is used by Duplica, she will make a comment that she would not make when using any other card.
In the manga
In The Electric Tale of Pikachu manga
Ditto in The Electric Tale of Pikachu
Ditto appears in The Electric Tale of Pikachu as the Pokémon of Duplica. Duplica used Ditto and its ability to transform to perform in a show in a Pokémon Center. After the show, Misty congratulates them on their great performance. Misty also showed extreme interest in catching a Ditto despite her being a Water-type Trainer, much to Ditto's nervousness.
While Ash, Brock, A.J. and the Samurai talk about a hidden village they plan on going to, Misty and Duplica go over to tell them that they intend on going out so Misty can catch a Ditto of her own. When Ash mocks her for wanting a Ditto, Misty has Ditto transform into a poor imitation of Ash, so she can beat him up, while acting like she has no idea which is which.
Ditto's habit of not transforming its face was originally presented as an anomaly. However, likely due to the popularity of the anime, it became associated as a feature of the Ditto species as a whole. Other Ditto with this trait have been seen in other media: