From the Super Mario Wiki
Roulette Blocks are types of blocks first found in Super Mario World. They are blocks that contain items that scroll in a roulette. The item the block displays while the block is hit is usually the item that comes out.
Super Mario series
Super Mario World
In Super Mario World, a Super Mushroom, Fire Flower, Cape Feather and Super Star can come out of a Roulette Block. However, once Mario or Luigi releases the item out of the block, it bounces around like a Star, but it still cycles from power-up to power-up. Mario or Luigi can grab the power-up at the right time to obtain that power-up's effects.
Super Mario Advance 4: Super Mario Bros. 3
A Roulette Block also appears in the Super Mario Bros. 3 Game Boy Advance remake, Super Mario Advance 4: Super Mario Bros. 3. It only appears in the level "Piped Full of Plants". It's very similar to the Super Mario World ones, but the Cape Feather is replaced by a Super Leaf. In addition, the item stops changing once released.
New Super Mario Bros.
Roulette Blocks reappear in New Super Mario Bros., but with a few differences. They are blue instead of transparent, the items scroll much faster, and they do not continue scrolling once they pop out - Mario must hit the block at the right time to make that item pop out. These Roulette Blocks can give Super Mushrooms, Fire Flowers, Super Stars, Mini Mushrooms or Blue Shells. Also, red Toad Houses contain giant Roulette Blocks (that contain the same items as the ones mentioned, besides the Super Star) which Mario can use to hold an item in reserve.
New Super Mario Bros. Wii
The Roulette Blocks from New Super Mario Bros. also appear in the sequel, New Super Mario Bros. Wii. The blocks are yellow this time, and they contain items such as a Super Mushroom, 1-Up Mushroom, Super Star, Propeller Mushroom, or Penguin Suit.
Super Mario 3D Land
The next appearance of Roulette Blocks is in Super Mario 3D Land, as transparent glass blocks, like in Super Mario World. They can now give Boomerang Flowers (from World 5 onwards) and Statue Leaves (in place of Super Leaves) in the Special Worlds. Winged Roulette Blocks can be found if Mario loses two lives in a row on a (skipped) normal world course.
New Super Mario Bros. 2
These blocks return in New Super Mario Bros. 2, with the same design as in Super Mario 3D Land. They can also now give Gold Flowers. In addition to the normal ones, gold numbered Roulette Blocks also appear, which produce coins instead of power-ups. When Mario hits the block, coins will pop out in the amount shown on the block when it was hit, either in single coins or 10 Gold Coins. The numbers that appear are 5, 10, 30 and 50, with 50 appearing only once per interval. Larger versions also exist, which can give 10, 50, or 100 coins (as a Giant Coin). In the Rainbow Courses, normal-sized coin Roulette Blocks only give 10, 30, or 50 coins..
New Super Mario Bros. U
Roulette Blocks also appear in New Super Mario Bros. U with the same functions as before, though they retain their New Super Mario Bros. Wii designs. They now have the possibility of generating a Super Acorn, an item introduced in the game.
Super Mario 3D World
Roulette Blocks reappear in Super Mario 3D World with the same look as in Super Mario 3D Land. They now have the possibility of generating a Super Bell, an item newly introduced in the game. Similar-looking Slot Blocks are introduced in this game in Lucky Houses, though they don't give items. Instead, they give coins depending on how many images are matched, from 10 (no matches) to 777 (four-of-a-kind) coins.
Super Mario World television series
A Roulette Block appeared in the Super Mario World television series in the episode "King Scoopa Koopa". After Princess Toadstool spots the Roulette Block and suggests that Mario should hit it, he hit the block and obtained a Cape Feather.
Mario Party 9
These blocks reappear in Mario Party 9 in the Sock It to Lakitu minigame. Here the items are a Bullet Bill, two Bullet Bills, three Bullet Bills and a Spiny Egg. The Bullet Bills damage Lakitu while the Spiny Egg may damage the player.
Mario Party: Island Tour
Roulette Blocks reappear in Mario Party: Island Tour in Bowser's Tower. They only appear after either making it to a certain floor or failing the same floor three times. A Roulette Block will then appear with one, two or three Mini Stars on it. Green Toad will then hit the block. The number of Mini Stars shown on the block will get rid of Bowser's minions in the next minigame. Getting three Mini Stars from the block skips the minigame entirely.
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