Dr. Fooler is a recurring antagonist from the Astro Boy franchise, appearing as a mad scientist whose schemes are typically more comical and lighthearted than genuinely threatening. His design is a deliberate choice to make him the least intimidating villain in the series. Physically, Dr. Fooler is a short, stout man, appearing to be in his fifties or sixties, though his stature and baby-like face make him look much younger. He is notably as short as the character Uran and is balding, with a single long, curly lock of hair on the top of his head. Despite his juvenile appearance, he dresses professionally, usually in formal three-piece suits, cravats, and bright white lab coats, and he often carries large canes or walking sticks that are taller than he is.

In terms of personality, Dr. Fooler is bombastic, incredibly self-assured, and seemingly completely unaware of his own unassuming stature. He is described as an unmanageable child who revels in creating a commotion, a crooked character who is agreeably underhanded rather than atrociously evil. His confidence is often his own worst enemy, leading to his schemes backfiring. While he is a talented scientist when he focuses, his creations are frequently poorly conceived and prone to causing disaster. Despite his villainous inclinations, he does have limits to the chaos he likes to cause and will reluctantly ask for help to fix his own schemes.

Dr. Fooler appears across various Astro Boy adaptations, each time with slightly different motivations. In the original manga and early anime series, he is a stingy and envious scientist with a one-sided rivalry with Professor Ochanomizu. His schemes are often petty and slapstick, such as building a robot duck designed solely to make loud noises and annoy the professor. In the 1980 series, he appears as a shady, for-profit scientist who created a robot safari in Africa, which he expanded to include a hunting range to make more money. His role in the story is consistently that of an antagonist, but his actions usually cause minor chaos rather than true danger.

In the context of Little Astro Boy, the 2003 anime series, Dr. Fooler is reimagined as a character named Dr. Minimini. In this version, he is an underground researcher specializing in micro machines. He presents himself as merely eccentric when visiting the Ministry of Science, but he and his assistant are secretly black market weapons dealers wanted by the police. Dr. Minimini becomes deeply interested in copying Astro's operating system, with the goal of reformatting and repackaging it to create an emotionless humanoid super weapon. His plan involves having his assistant implant a robot virus into Uran to promote his own technology as a solution. He also uses his machinery to clone Astro into a tiny, functioning model. His ultimate scheme is to escape with the full-sized Astro's body in his machine, which would leave the hero trapped as a tiny toy while still fighting the virus. The miniature Astro ultimately destroys his machine, leading to Dr. Minimini's arrest by Inspector Tawashi.

Key relationships for Dr. Fooler include his frequent, one-sided rivalry with Professor Ochanomizu, whom he envies. In the 2003 series, his relationship is primarily with his unnamed assistant, who aids him in his criminal activities, and his adversarial dynamic with Astro. Information regarding his character development across the series is not available. For notable abilities, Dr. Fooler is a skilled scientist, particularly with a specialty in micro-machine technology in his 2003 incarnation. His other notable trait is his overweening ego, which consistently undermines his own plans.