Flemming, often referred to as MC JF, is a character in Marie & Gali who is based on the historical British physicist and electrical engineer John Ambrose Fleming. He appears as a resident of the mysterious town of Garihabara, where he operates a ramen cart that can be transformed into a mobile DJ station. Flemming is depicted with a deep passion for hip-hop music and culture, incorporating rap and turntable performances into his daily life and scientific teaching methods. His personality is energetic, theatrical, and performance-driven, using music and rhythm as his primary means of expression. Unlike the more cantankerous and slapstick-prone Galileo (Gali), Flemming is generally casual and cool-headed, though he fully embraces the show's over-the-top and surreal comedic style.

In the story, Flemming's primary role is to introduce scientific concepts related to electromagnetism, particularly Fleming's left-hand rule for motors, which determines the direction of force on a current-carrying wire in a magnetic field. He teaches these lessons not through lectures but through original hip-hop songs and dance routines. For example, his Love Coil song and accompanying performance are designed to explain the relationship between current, magnetic fields, and motion in a way that is accessible to the middle school protagonist, Marika. This method proves so effective and stimulating that it can also be used to induce sleep through mental exhaustion. In one instance, after Marika suffers from insomnia, Flemming's complex explanation and high-energy demonstration cause her to become dizzy and immediately fall asleep, illustrating the show's quirky blend of education and comedy.

Flemming maintains a friendly and cooperative relationship with Gali, often serving as a collaborator in schemes and musical interludes. Marika views him as a strange but reliable source of scientific knowledge within the town's eccentric community. He is also shown interacting with other historical scientist residents, such as Archimedes, and is occasionally used by others, like Gali, to help settle debts or pull pranks. Flemming does not undergo significant personal development within the series, as his function is largely episodic, providing musical educational segments that reinforce the show's central theme of making science fun and memorable. However, his consistent enthusiasm and talent for breaking down complex physics into catchy, rhythmic lessons establish his definitive role in Garihabara.

His most notable ability is the fusion of scientific demonstration with musical performance, specifically using turntables and rapping to act out physical laws. This talent allows him to transform his ramen cart into a complete stage setup and command the attention of other characters. Flemming effectively personifies the connection between the left-hand rule and the posture of a hip-hop artist, making the abstract concept of motor function physically intuitive and entertaining.