A big figure in the Smash speculation community, named Mimique, had a pretty crazy theory. Piranha Plant, Mii Swordfighter, and Duck Hunt all seem to have a connection with that glitch in the 2.0 version. The theory is that they're glitching out because Mii SF is being used as a base for this possible Dragon Quest rep, as they would obviously be a sword character, and that Duck Hunt is being used as a base for Banjo and Kazooie, which is affecting the game firmware somehow. This same thing happened with Smash 4, as Bayonetta uses Zero Suit Samus as a base. This is coupled with IndieGamerChick's rumors. It's pretty far out there, but stranger things have happened before. Its really strange that all three of those characters glitch out like that, I'll say that, at the very least.