My Neighbour The Groke
by Slidesalaten on pixiv
One of the best episodes.
She also makes an appearance in the later episodes, when Moomin spends a winter without hibernating, alone.
If we're talking about the 90s anime adaptation.
Not sure about anime, but definitely 90s. And I remember that episode! I completely forgot! I gotta find my VHS tapes. And the VHS player, I suppose. Possibly the best show from my childhood. Learned a lot of life lessons from it.