Gentoo Penguin, an anthropomorphic character based on the real gentoo penguin species, uses nicknames including Gean, Gen, Jen, or Jane. She possesses long black hair extending to her waist, with orange highlights in her bangs evoking a penguin's beak. Her amber-colored eyes match the circles on her earphones. She dons a windbreaker-style jacket mirroring gentoo penguin plumage, a white skirt, yellow boots with mitten-like sleeves covering her hands, and distinctive white headphones. A prominent long tail matching her hair color completes her appearance.

As a member of the Penguins Performance Project idol group, she consistently demonstrates a formal, courteous personality, embodying the group's "orthodox idol" archetype. Her modest, respectful demeanor includes polite speech patterns even with close associates. Though reserved and susceptible to stress, she exhibits strong dedication to singing and dancing performances.

Her role remains consistent across media. During a Season 2, Episode 1 post-credits scene with fellow PPP members, Suri Alpaca presents coffee jelly, prompting Gentoo Penguin to inquire about the dessert. As Hululu mixes the jelly, she reacts by covering her mouth while other penguins show visible shock. She subsequently calms, requests to taste the mixture with the group, and joins their collective introduction of the next episode's title.

Real-world gentoo penguin traits inform her characterization: They build stone nests, display territorial behavior over stones, rank as the third-largest penguin species globally, and swim at speeds nearing 36 kilometers per hour. These parallels reflect her meticulousness and performance dedication.