its hard for me to pick one, but i can slim it down to a few favorites
mystery train, the creeps, holly jolly secrets(both parts) and min and marty
all of these are very close but i think i can say min and marty is my favorite.. for me its such a deeply sad yet comforting episode. still its very close with the other episodes
honorable mentions are memories of boom boom mountain, the episode with the king worn(cant remember its name, abstract, and the wild hunt...
at is like my fave show oat so its hard to be definative about this kind ofstuff