? Coin

A Question Coin is a special Coin found in Super Mario Galaxy and Super Mario Galaxy 2. Question Coins appear in many galaxies throughout both games. When one is collected, it could cause any of the following things to appear:
 * A trail of Rainbow Notes.
 * A large amount of Star Bits or Coins.
 * A Power-up.
 * A Sling Star.
 * Another Question Coin.

Most of the time, Mario is given a time limit to collect whatever appears and if he is able to successfully collect it within the time limit, he will receive a prize. Most likely, it will be one 1-Up Mushroom, but it is also possible for it to be three 1-Up Mushrooms, a Power-up, more coins or Star Bits or, very rarely, a Rainbow Star.