Kōmori (こうもり, meaning "Bat") are, as their name explains, bat creatures, which star in Mario vs. Donkey Kong as enemies. They fly horizontally and across the level's room, making a small descent and changing direction whenever they encounter one of the room's margins. They can usually be seen travelling past ropes, and they spawn from small roosts.
Whenever Kōmori fly into Mario, they hang onto and throttle him, causing Mario to fall off the rope he is currently climbing. Mario can either survive crashing onto the ground or lose a life, depending on the height reached where the bat enemies intercepted him.
They did not reappear in the sequels, having been replaced by Swoopers.