Meteor Ghost

Meteor Ghosts are ghosts that can be found by Luigi only in the Observatory of Luigi's Mansion.

Story
When Luigi first enters the Observatory, the first thing he notices is a small telescope. Luigi can then walk towards it and get a better look. When he looks through, he notices a small moon; at which point the Meteor Ghosts try to attack. Luigi is able to suck a Meteor Ghost into the slot of his Poltergust 3000. He can then fire it at the moon, causing the it to explode, revealing a path to Mario's Star.

Trivia

 * Luigi does not lose any HP if he is hit by a Meteor Ghost, making it one of two types of ghosts in-game which cannot deal damage, the other being Ceiling Surprises.