Daisy and Waluigi were intended to be unlockable characters at one point. They are made available from the beginning in the final release.
Unused story mode rankings exist in the game's data for ranks D, E and F. In the final game, the lowest anyone can get in Story Mode is C.
After failing an item minigame in the Japanese version, the announcer will say "Miss". But in the international versions the announcer says "Game Over". The clip itself can still be heard in the voice test option in the Sound Room.