Giant Red Shell
From the Super Mario Wiki, the Mario encyclopedia
Giant Red Shells are items found in some Mario games. In Super Mario Bros. 3, Red Giant Koopa Troopas wear these giant shells; Mario or Luigi can jump on these oversized Koopas, making them retreat in their shell. As with other Koopa shells, they can also be picked up and kicked.
In Super Mario Maker, Super Mario Maker for Nintendo 3DS, and Super Mario Maker 2, if the player shakes a green Koopa Troopa and turns it red, then give it a Super Mushroom, it will turn into a Big Red Koopa Troopa, and when stomped on, will hide in its shell. These shells work as they do in the New Super Mario Bros. games, though they can also break through Hard Blocks without bouncing off, but they cannot be picked up.
Giant Red Shells make a return in the Mario Strikers series as an item, along with their smaller counterparts. Working similarly to their smaller counterparts from the Mario Kart series, they can be collected and fired. The item homes into opposing team members, squishing and stunning them for a short while. After hitting its target, it randomly bounces around the stage until it wears out.