Momoko's design changed noticeably as the series progressed—she went from brown-haired in the second series to purple-haired by the third and fourth, and aged up to match Chibiusa when the latter returned, both shifts happening without any explanation.
Her first real moment in the story came during the Black Moon arc, when she got caught between two droids, Chiral and Achiral. The fight left her badly hurt, which sent Chibiusa into a panic and triggered her latent powers to burst out against the monsters.
Later, during the Dead Moon Circus arc, Momoko became the Amazoness Quartet's first target. She went to see the circus's opening show with Chibiusa and Kyūsuke, where Flower Magician CereCere put her under a spell. Hypnotized and separated from the group, she was attacked by the quartet. When they checked her dream mirror and found it wasn't the Golden Dream Mirror they were after, they summoned a Lemures to consume it. Sailor Chibi Moon and Sailor Moon showed up to save her before things got worse.
Content compiled by AnimeList.moe from publicly available sources.
