Marshall Lee (full title Marshall Lee the Vampire King), is the gender-swapped version of Marceline, created by the original series designer, Natasha Allegri and featured in "Fionna and Cake." Cake is scared of him just like Jake was scared of Marceline.
Marshall Lee has pointy ears and light blue skin. An alternate character sheet depicts him with green skin, but it was only used in one scene with a special lighting.
His hair is shorter than Marceline's but he has a matching permanent bite mark. He initially wore a grey plaid shirt, but now wears a red and black plaid shirt. He also wears dark blue jeans, and brownish-white sneakers.
Though Marceline has circle-shaped eyes, his eyes are rectangular. Unlike Marceline's forked, snake-like tongue, Marshall Lee's tongue is rounded.
So far, Marshall Lee has appeared in three 'Fionna and Cake episodes'. In 'Fionna and Cake, he was shown giving Fionna the 'rock salute' and sticking his tongue out at her at Prince Gumball's ball. In 'Bad Little Boy', he is a major character and brings Fionna to sing with him at LSP's party and later, he captures Cake, enraging Fionna. Then, he fakes his death by sticking a stake in his shirt while his shirt was filled with cream puffs. In 'The Prince Who Wanted Everything', he was one of LSP's servants, for a short time, along with Prince Gumball, Turtle Prince and Flame Prince.