Meetenda Island, a feminine portmanteau of "Mii" and "Nintendo," at least it's supposed to be (It's torture having to deal with pronunciations in this game).
Grandiose Island, from the French word for Grand, because I knew a grand amount of stupid stuff was going to happen there.
My Mom's friend has the game and named her island 'Asslandia', so I'm actually kind of jealous I couldn't come up with something as hilarious as that.