Dokin-chan is a germ originating from the planet of germs. She appears orange-red with a white face, green eyes, small red cheeks and nose, pink shoes, white hands, a single antenna, and a long tail resembling other germ characters. Primarily serving as Baikinman's partner and a secondary antagonist, she frequently participates in his schemes. Her personality is selfish, demanding, childish, and greedy, often bossing Baikinman around and ordering him to fetch things. She displays cowardice, typically fleeing first when confrontations turn unfavorable. Despite her antagonism, she occasionally shows kindness, driven by an intense romantic obsession with Shokupanman that began during a bread theft incident. This infatuation leads her to extreme efforts to win his affection, including maintaining a room filled with Shokupanman posters and plush toys and frequently daydreaming about romantic scenarios with him.

Her relationships are complex. While she works with Baikinman, their dynamic involves her frequent rudeness and demands, though an underlying care exists. Her interactions with her younger sister, Kokin-chan, fluctuate between camaraderie and rivalry, fueled by their shared affection for Shokupanman. Dokin-chan utilizes specialized equipment, including a staff capable of enlarging or shrinking objects it touches, though its use diminished over time. She also operates a pink UFO, primarily for transportation or holding hostages during schemes rather than direct combat. Her name combines "Doki" (Japanese onomatopoeia for a heartbeat), "baikin" (germ), and the diminutive suffix "-chan," reflecting her romantic inclinations and germ origins. Alternative international names include Spark (English TMS Entertainment/Cinar dub), Dokeen (Tubi English dub), "红精灵" (Red Spirit in Chinese), and "짤랑" (Jingle in Korean).