? Coin

A Mystery Coin is a special Coin in Super Mario Galaxy. When one is obtained one of the following occurs:

They appear in few stages, like Good Egg Galaxy.
 * A Mario theme will play and a line of musical notes will appear for Mario to collect, usually causing a 1-Up Mushroom to appear.
 * An accumulation of Star Bits or Coins will appear for Mario to collect.
 * A power-up will appear.
 * Another Mystery coin will appear