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 plumbers make. Boards usually warn the plumbers that Cosmic Clones are present in the area, although the also appear when a Prankster Comet orbits in a galaxy. 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 changed. If Mario or Luigi gets hit by one clone, he receives damage and the clone vanishes (which then the rest of the clones will mimic the plumbers from being damaged). Once the way out of the area where Mario or Luigi is in is revealed, they disappear screaming loudly for a few seconds and leaving behind a multiple of three Star Bits each one.

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.