Schwabelle is the gender swapped version of Marceline's zombie dog, Schwabel. However, Schwabelle is a zombie cat and she belongs to Marshall Lee.
Marshall Lee- She seems to be quite close to Marshall Lee. She is seen sitting on top of Marshall Lee's head in this picture.
Mortuus- Mortuus is Marshall Lee's other zombie cat. They seem to get along quite well.
Schwabelle, despite being a zombie, she looks like a regular cat. She has white fur, dots for eyes and a bushy tail.
Schwabelle has yet to appear in an episode of Adventure Time.