Cosmic Clone

Cosmic Clones (or Shadow Clones) are shadowy duplicates of Mario or Luigi that appear in Super Mario Galaxy 2. Cosmic Clones are created once a certain point is reached in a galaxy and will follow behind Mario or Luigi, performing every movement the plumber makes. Once the way out of the area Mario is in is revealed, they will disappear, leaving behind a multiple of 3 Star Bits. If Mario touches a clone, he will take damage, so horizontal movement is necessary for survival. Boards usually warn the plumber that Cosmic Clones are present in the area. Cosmic Clones also are able to walk where there is no platform if it is necessary for following Mario. Also, Cosmic Clones will do whatever Mario did, even if the landscape has recently been change. Upon contact the single cosmic clone dies, so if there is only a certain amount Mario can kill them all by walking into them though taking damage. Once the Cosmic Clones vanish, due to the requirements of a galaxy being met, they scream for a few seconds.

Trivia

 * The Cosmic Clone's theme is a remix of the Super Mario Bros. overworld and underground theme, like Cosmic Mario's (or Cosmic Luigi's) theme from the prequel.
 * Cosmic Clones also share the same tone of voice as Cosmic Mario's and Cosmic Luigi's: a high-pitched voice that is strikingly similar to Bowser Jr.'s, and another trait is that Cosmic Clones look like Cosmic Mario or Luigi, but Cosmic Mario or Luigi cannot hurt the brothers, and they have a starry display and their bodies are blue.
 * Another noteworthy thing is that Cosmic Clones, perhaps the reason that Cosmic Clones will follow Mario or Luigi anywhere, they obviously are not too bright, this is because if Mario or Luigi fall from the stage, they will do so.