Also known as: ムーミンほっぽ, むっぽちゃん
Due to the way that Twitter makes thumbnails, a certain comic's last panel made Northern Ocean Princess look like Moomintroll, and so a legend was born.
As indicated above, Muppo is a mash-up between Northern Ocean Princess and a Moomin created by Sazanami Konami. She (?) has Hoppo's hair, horns (in place of a Moomin's ears), spiked collar, anklets and mittens while the rest is generic Moomintroll stuff.
She is noted to be extremely unlucky and/or clumsy. Most of her series (pool #9684) has her failing at everyday tasks. Seems to like Mayonnaise.