She first appears in the second series with brown hair, but her character design is modified in the third and fourth series to have purple hair. She also jumps up in age to match Chibiusa's new age when she comes back in S. Both occur with no explanation.
Her first appearance in the series (In R) had her caught up in a fight with Chiral and Achiral, two Black Moon Droids, and badly injured as a result causing ChibiUsa to go into a fit and unleash her latent powers at the monsters.
Momoko is the first target of the Amazoness Quartet in the anime. When she goes to see the first performance of the Dead Moon Circus with Chibiusa and Kyūsuke, she falls victim to a spell cast by Flower Magician CereCere. In a hypnotic trance, she leaves her seat and is attacked by the Amazoness Quartet. Once her dream mirror is revealed and not the Golden Dream Mirror sought by Queen Nehellennia, the quartet summon a Lemures to devour Momoko's mirror. She is saved by Sailor Chibi Moon and Sailor Moon.