This shouldn't be seen as such an oddball choice after you consider what a massive success Wii Fit was, and how important a franchise it now is. Just like with the Animal Crossing Villager, they're clearly making sure to represent all their big name franchises with playable fighters (I wouldn't be entirely shocked to see Dr. Kawashima from Brain Age either at this point.) I am a little surprised by the actual choice of representative-- I would have assumed they would have gone with the Wii Balance Board character, but she/he/it does appear alongside her in the video so will likely still be used somehow in her move set.