Penelope, known in the original Japanese version as Chibimaru-chan, is a young hamster in the anime Hamtaro. She is a small white-and-brown baby hamster and the youngest member of the Ham-Ham gang, the group of hamsters around whom the stories revolve. She is owned by a girl named Kylie and lives in the same neighborhood as the other Ham-Hams. Her most recognizable trait is the yellow blanket she wears over her head, which she uses to hide because she is very shy; she is almost never seen without it, although it occasionally slips off.

In terms of personality, Penelope is shy, gentle, innocent, and naive. Because she is still a baby, she does not fully understand everything that happens around her, but she is friendly toward everyone and is an accepted and cared-for member of the group. She does not yet speak in full words; her vocabulary mainly consists of sounds such as Ookwee and Ookyoo, but the other Ham-Hams can understand what she means. Her main way of learning about the world is imitation. This is shown in an episode in which the Ham-Hams' belongings suddenly go missing, and it is discovered that Penelope took them because she was copying what the others did. She did not intend any mischief; mimicking others is simply how she learns.

Her most important relationship is with Pashmina, an older hamster who looks after her. Penelope views Pashmina as an older sister, and the two are best friends, with some English-language materials even describing them as sisters. Because she is so small and young, she is looked after by the older members of the group. In one episode, Penelope Makes a Friend, she meets a young character named Ethan and immediately takes a liking to him; she wants to give him a gift to show that he is her new best friend, though her shyness makes it hard for her to express this. Her motivations center on closeness and belonging: she wants to be near those she admires, behave like them, and form bonds of friendship.

Within the story, Penelope fills the role of the baby of the group. She takes part in the Ham-Hams' activities and appears in the television series as well as in the franchise's films, usually as the smallest and most protected member. Since she is still very young, her development is shown through her gradual progress in learning to talk and through the small moments in which she comes out of her shell. In the earliest versions of the original source material, the character was initially presented as a boy and called Chibimaru-kun; the anime version instead presents her as a girl. Her notable traits include her tiny size, her limited but meaningful way of communicating that her friends understand, and the yellow blanket that serves as both a shy disguise and a source of comfort.