Rock Pikmin are a unique species of Pikmin introduced in the game 'Pikmin 3.' Unlike other Pikmin, their bodies are hard and crystalline, resembling small rocks. This gives them the special ability to break glass and crystal barriers that other Pikmin cannot destroy. They are immune to being crushed and deal more damage when thrown at enemies. Rock Pikmin play a crucial role in puzzle-solving and combat throughout the series, helping the main characters progress in their exploration and rescue missions.