Munny is the currency used throughout the Kingdom Hearts series. Munny originally resembled a rounded octahedron, but later appeared with sharper angles. It is generally obtained by killing non-boss enemies such as Heartless and Nobodies, or by selling off unwanted items. Similarly munny is used to purchase items from shops. Munny comes in three sizes, with each size worth either one, five, or twenty munny.
Roxas and his friends in the Simulated Twilight Town spend the second day earning Munny for a trip to the beach by doing odd jobs. However, once they go to buy the tickets, Riku bumps into Roxas and snatches the Munny Pouch, since the beach had not been programmed into the simulation.
This Munny Pouch filled with Roxas's hard-earned Munny is later given to Sora, although the pouch is treated as a Key Item, and therefore the Munny within the Munny Pouch cannot be spent, or otherwise used for any purpose.
Munny dropped by enemies is affected by Jackpot, which increases the amount, and Treasure Magnet, which makes it easier to collect. Lucky Strike and Encounter Plus also help in making munny (by letting you sell excess items and encounter enemies faster). At the end of the game you can best acquire munny by going through the Third District in Traverse Town and destroying the enemies as fast as possible.
Other than fighting enemies you can also acquire munny from a few Trinity Marks, and the Bouncywild's banana peel also forces anything that slips on it to drop munny. The Mystery Mold dropped by Black Fungus also sells for 9999 munny, but it only rarely drops if they are slain with a critical hit.