Pinhead

Pinheads are enemies that appear in Super Mario Galaxy 2. They look like bowling pins and have 2 beady eyes and a bright yellow antenna. They can only be defeated when Mario is transformed into Rock Mario. When Mario walks over to them, they hide in holes underneath themselves. But, when he is Rock Mario, they get scared and tremble. These are rare enemies, for they only appear in Boulder Bowl Galaxy and Melty Monster Galaxy.

Trivia

 * When Rock Mario hits some Pinheads, it's similar to bowling. Rock Mario is meant to be the bowling ball, and the Pinheads are meant to be the bowling pins.
 * Pinheads most likely got their names from bowling pins, as that is what they're meant to be.