Marshall Lee, is the gender-swapped version of Marceline, created by the original series designer, Natasha Allegri, who is featured in "Fionna and Cake". In the episode, he is seen attending Prince Gumball's Biennial Gumball Ball.
In honor of the spooky season, here are what fictional characters do for Halloween. Credits of Fanart: Luxojr888 https://www.deviantart.com/luxojr888/art/FOR-CANDY-Happy-Halloween-2018-770634899
