From Bulbapedia, the community-driven Pokémon encyclopedia.
Mirror Bonnie (Japanese: 鏡の国ユリーカ Mirror World Eureka) is a doppelgänger of Bonnie and a character of the day who appeared in The Cave of Mirrors!. She is Bonnie's counterpart from the Mirror World, whose personality is opposite to that of the regular Bonnie, as she has lady-like mannerisms and is proud of her brother and his achievements. In the English dub, she speaks with a refined, English accent.
After Mirror Ash lost a battle against Mirror Serena, he ran off crying, stating he would travel alone onward. The Mirror World counterparts of Bonnie, Clemont, and Serena went looking for him and found him just outside Reflection Cave. What they didn't know, however, was that this was the Ash from the regular world instead. As the group started to notice how Ash's personality was different from the Ash they knew, Mirror Clemont deduced this was an Ash from another world, according to a legend that the Reflection Cave harbors portals to other worlds.
Mirror Serena refused to believe this, and challenged the regular Ash to a battle. After the battle, Mirror Ash showed up, having watched the battle from behind a tree. When Mirror Ash told he lost his Pikachu, the group and the regular Ash decided to go look for him. Mirror Clemont then proposed to use his magic to find Pikachu. Mirror Bonnie showed her excitement at her brother's trick, and even though they wound up in a dead end, she just casually stated that everybody makes mistakes.
Later, Mirror Bonnie and the rest of the group helped in getting the regular Ash back to his own world. They found the mirror through which the regular Ash had come, and managed to get the portal to appear. As the portals of the regular world and the Mirror World started to drift further apart, Mirror Bonnie encouraged her regular counterpart, who was at the other portal, to wish strongly for Ash to return. The regular Ash ultimately managed to get back, and Mirror Bonnie said her farewells as the portals closed.
Taking care of
|| Dedenne ♂
| Like the Bonnie of the regular world, Mirror Bonnie takes care of her brother's Dedenne and carries him around in her pouch. Not much is known about how much Mirror Dedenne's personality differs from the regular world's Dedenne.
None of Dedenne's moves are known.
|| The Cave of Mirrors!
| Voice actors
|| Megumi Satou
|| Megumi Satou