Piranha Plant's side special, Poison Breath, seems to come from the Paper Mario series, specifically from the Putrid Piranhas from Paper Mario: The Thousand-Year Door. Piranha Plant's "bud" even changes color to match a Putrid Piranha's yellow and red color scheme during the attack. This would make Piranha Plant the only Mario series character to have a move derived from the Paper Mario series.
Contributed by PirateGoofy