Icy Rocktor

The Icy Rocktor is exactly like other plug-bugs; a strange, worm-like creature that wears a helmet made of rocks and lives inside cave entrances. A cave that is plugged up by a Rocktor cannot be entered until the creature is defeated. The Icy Rocktor, if approached, will periodically cover its den with its rock helmet and scatter snowballs around by shaking itself. The snowballs will freeze all but Cyan Pikmin, so those are recommended for fighting these enemies. When defeated, the Rocktor's helmet shatters and it falls into the cave below, allowing access.

In Pikmin X: Deep Freeze
These enemies can be found blocking tunnels that Pikmin can dig through, and will try to scare off Pikmin by tossing snow around to freeze them solid. Rock Pikmin can shatter its crystal helmet and leave it stunned for a few seconds, preventing it from shielding itself by plugging up the hole.