Dark Koopas are purple Koopa Troopas that lurk underground and in caves. They are part of the underground Koopa Troop. These "shy guys" move slower than normal Koopas.
Compare and Contrast
Crayzee Dayzees can be as fast as them. Like Gloombas, they are colored darkly due to lacking sunlight. Dark Lakitus also imply the same way.
- Despite living in darkness, it's skin color is not darker, compared to Gloombas