Red Arremer
Member
Wii Fit Trainer's a nobody.
Wii Fit Trainer is a character from a recent game series that had yet to be introduced into Smash, out of which both installments sold significantly more than Majora's Mask did. Her series had its last installment in 2009, and also is going to get a new game come December this year.
Skullkid was important in a single game in 2000 on a system 3 console generations ago, and other than the VC port, has only appeared as a minor antagonist in Twilight Princess (classified as "mini boss" even), which also is outdated.
Out of all the minor Zelda baddies, I'd say Ghirahim, and even Vaati and Zant all have better chances than Skullkid.
Same could be said for Isaac from Golden Sun, but I'm sure many would also argue he's a nobody, heh.
Golden Sun is but a blip in comparison to Wii Fit. I would agree that Isaac is a nobody, perhaps even more than Skullkid. However, unlike Skullkid, there's not really any other characters that are more significant in his own series than he is. If anything, about the same level.