Schwabl is Marceline's dog who was first shown in "It Came from the Nightosphere." He is apparently an old dog of her's, he hasn't had much of a role in the series. He is apparently a zombie poodle now.
He is a white poodle with big black eyes and a black nose. He doesn't have a lower jaw, which is covered by his fluffy beard and a skinny tail with a puff of hair at the tip of the tail. It is similar to a bunny, but without the tail.