

Marshall Lee is first seen interacting with Fionna in "Bad Little Boy." There, he is seen doing bad things to convince her that he is evil, while also trying to get her to admit that she loves him. Marshall Lee also occasionally flirts with Fionna as seen in "Bad Little Boy", though this seems to contradict Marceline's claims to only liking Finn as a friend. This also might suggest that Marceline wishes she could express remorse better she rarely apologizes to anyone. Since Marceline is telling his story at this point, this might suggest the way she thinks of herself as a villian, although Marshall Lee is argueably the more evil of the two. He also displays Marceline's love to mess with people with elaborate jokes, but goes to a further extent than his female counterpart and feels remorse quicker. He appears to have an interest in music like Marceline, as he's shown to rap and carry around and play a custom bass guitar, like Marceline. He greeted Fionna with the sign of the horns, a very popular hand sign amongst heavy metal and rock fans. He is rowdy, endangering others with his violent, 'friendly' rough-housing. Marshall Lee describes himself as a villain. Marshall Lee can also be seen with his bass guitar strapped on to his back by his lucky-red guitar strap, although he has once held his hand out, and the bass comes out of no-where and flies into his hand(like Thor). Like Marceline, his physical appearance is that of a typical late teenager. In "Fionna and Cake" and "Bad Little Boy," he is seen wearing a red plaid shirt with gray stripes, dark blue jeans, and brownish-red and white sneakers. He has a matching permanent bite mark like Marceline's. Marshall Lee has a slim body, an average height(5'11), black hair, and light green skin. He also appears to have the same rapid healing that Marceline has, as when the sun started to burn him, the burn vanished as soon as Cake blocked it from touching him. Like Marceline, he can also raise the dead.

He can turn into a bat form, like Marceline, except he keeps his hair. Some official artwork shows him eating the color red, just like Marceline, and sucks the pink from creme puff filling although he says he drinks blood in "Bad Little Boy". Marshall Lee presumably has the same abilities as Marceline, since he was first seen floating.
