[Random]

That's not quite how it works, it isn't a popularity contest. They're just looking for suggestions and will include ones they think will work best. Even if every single person voted for Shrek, it's still (probably) not going to happen. I imagine they're going to have a lot of kids submitting ideas for characters like Master Chief which obviously aren't going to work either, so you know some suggestions will be filtered to go straight in the trash.

Characters who are unique, owned by Nintendo and are well known have the most chance of being added and giving reasons for them to be there besides "this would be so cool/badass!!1" will probably help a lot too.