Well, they lock some characters to Amiibo. You can't get Rosalina or Toad unless you play as their Amiibo, and it was probably a coincidence since I didn't play very long before using Amiibos, but DK and Diddy didn't appear until after I used their Amiibos. I got really lucky with my Amiibos though. I went to GameStop and they had all 7 of the new MP ones, plus Pit and Robin, so that was cool!