From the Super Mario Wiki
Dark Paratroopas (or D. Paratroopa) are purple Paratroopas that live in the Pit of 100 Trials, in Paper Mario: The Thousand-Year Door. They are basically Dark Koopas with wings. These are stronger versions of regular Paratroopas, having more HP and Attack. Jumping on a Dark Paratroopa causes it to lose its wings and become a Dark Koopa.
Dark Paratroopas were originally going to be in the original Paper Mario, but were removed from the game. However, their coding was not, and this includes a complete Goombario Tattle, which means the stats are intact as well.
Paper Mario unused data
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