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Coin Stacks are items that appear in Super Mario 3D World. Coin Stacks are ordinary Coins that are stacked up in piles that each have different amounts; the coins act as they normally do, giving an extra life for collecting 100 of them. Coin Stacks can be found in hidden areas of levels, like in the underground area of Really Rolling Hills. They are a very common item in the bonus level Coin Express, where they appear alongside of Coins, Gold Rings, and Gold Shells.
Coin Stacks will appear in Super Mario Odyssey, acting as they did in Super Mario 3D World. They can also come out of bushes, causing them to bounce along the ground in an erratic fashion, like Super Stars.