In Miitopia, you've got a quest, a hero, a kingdom, and a bunch of monsters to pummel, in the most deliberately generic storyline this side of Final Fantasy: Mystic Quest. The hook is that you can recast all of the human characters, from your hero to the ultimate villain, via Nintendo's Mii character creator.
“The word I want to use here is ‘harmless.’”
It comes pre-loaded with an assortment of copyright-infringing, user-created avatars, but there's a lot of fun to be had with making your own and throwing them into (in)appropriate positions in the kingdom.