Caterpillars are enemies introduced in level 13 of Gravity Duck.
The caterpillars in Gravity Duck are red with four body segments. They have a visible white eye and short dark coloured lines sticking out of each of the segments. The two lines in the middle are slightly the longer than the ones on the outer part of the caterpillar.
Caterpillars are always seen facing sideways from the player's perspective. They are often found pacing around on the flat surface of walls, ceilings or the ground. As they move, their body length constantly shortens and widens, causing their height to fluctuate as well. Using this motion, caterpillars move along the surface they are placed on until they reach a corner or a wall that prevents them from going farther. They then turn around and move in the opposite direction. Caterpillars never turn corners, and one will only inch along on a single plane at a time.
Upon contact with a caterpillar, the duck explodes and the player is forced to restart the level. As with all enemies in the game, they cannot be killed or damaged in any way.