Giant ? Block
From the Super Mario Wiki
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Giant ? Blocks (or Giant Question Blocks) are ? Blocks that are twice as big, first found in Super Mario Bros. 3 and its remakes. They are found mainly in the game's World 4 (Giant Land), but can also be found in certain secret areas throughout the game. They contain regular power-ups or coins in Giant Land, and three 1-Up Mushrooms or one of the game's three Suits (the Tanooki, Frog, and Hammer Suits) in bonus areas. While they couldn't be tail whipped at all in the NES and All-Stars versions, Super Mario Advance 4 makes it so Raccoon or Tanooki Mario can tail whip Giant ? Blocks in normal courses.