Some time ago, Duplica and Ditto were making shows, where Ditto used Transform to impersonate other Pokémon. It did not go well, as Ditto did not copy the Pokémon's face, instead retaining its own.
When Ash, Brock and Misty came into the mansion, they saw Duplica, imitating Ash, whose Ditto was impersonating Pikachu. Ash demanded a match, sending out Bulbasaur, but Duplica's Ditto transformed into Bulbasaur and, using a different move, defeated it. Though Ditto was captured by Team Rocket, Duplica thanked Jessie, James and Meowth as Ditto had its face corrected when using Transform. After the matter was resolved, Duplica was glad she could run her theatre once more.
She later appeared as a Nurse Joy, then took off her disguise (after Brock realized she was not the real Nurse Joy), revealing herself as Duplica to the heroes. She showed the heroes her Mini-Dit, which could transform into any Pokémon, but remained at a small size. Team Rocket captured it and planned on selling and retrieving it, but Mini-Dit came back to Duplica. Team Rocket fought her and Ash, but were defeated. Duplica decided to keep the Mini-Dit and have a team of Ditto, then bid farewell to the heroes.
Ditto is Duplica's first Ditto and her trusted partner. They perform cosplay shows together, and now that Ditto can transform perfectly, their business has gone up. However, they did have a rocky start when Ditto could not transform. After Team Rocket's interrogation, Ditto managed to overcome this problema and could transform fully.
Mini-Dit is Duplica's second Ditto. It was caught shortly after Duplica parted ways with Ash and his friends. However, it has a problem in that it can transform into other Pokémon, but it is only seven inches tall.