Baikinman hails from Baikin Planet, arriving on Earth as an egg that hatched simultaneously with Anpanman's birth, forging their intrinsic rivalry from inception. His design manifests as an anthropomorphic germ with fly-like attributes: wings, antennas, a zigzag tail, purple lips, and a slimy blue tongue. Exposure to soap triggers a transformative weakness, causing his black furry body to shrink and bleach white.

Personality traits encompass pronounced narcissism, impulsiveness, and a self-proclaimed genius intellect, frequently channeled into elaborate mechanical inventions designed to defeat Anpanman. Despite his antagonist role, he displays resilience through repeated defeats and moments of vulnerability. Creator Takashi Yanase indicated an underlying desire for normalcy conflicted by his predetermined path. His primary motivations involve sabotaging Anpanman, stealing food as a glutton, and propagating germ-based chaos, though he sporadically assists Anpanman against greater threats.

Defining relationships shape his character:
- Anpanman stands as his fated nemesis, though their dynamic includes reluctant cooperation and non-adversarial interactions outside direct conflict.
- Dokin-chan serves as his frequent partner; Baikinman harbors unrequited affection for her despite her preference for Shokupanman.
- Franken Robo-kun, a robot he created, views him as a paternal figure. Baikinman exhibits a distinct soft spot for him despite initial avoidance due to accidental electrocutions.
- Rollpanna, influenced by his "Baikin Plant" implantation, alternates between aiding his schemes and betraying him to support Anpanman.

His cultural impact includes inspiring germ-personification tropes in Japanese media, notably influencing the concept of Pokémon's Team Rocket. The character also inspired parodies such as Vaccine Man in *One-Punch Man*, sharing the same voice actor.