If you comlete criteria for unlocking more than one character, do you fight both (one after the other)? For example, I believe you unlock Sonic after 10 Classic mode run-throughs. And I think that you unlock Toon Link after 1 Classic mode run-through with Link. So if it was your tenth Classic-mode run through, and you were playing as Link (assuming you hadn't already unlocked Toon Link), would you fight Sonic and Toon Link? Or would it just be one of them, and then you have to repeat for the other?
I know that's a bit wordy, but I hope I got my point across.