The Perpetual Shell
From the Super Mario Wiki, the Mario encyclopedia
As in all Boost Mode challenges, one player controls the character on the television screen while the other player uses the Wii U GamePad to place Boost Blocks that will help the character. The player must stomp a Koopa Troopa and use its shell to hit as many Goombas and Goombrats as possible, earning 1-Ups while using Boost Blocks placed by the player using the GamePad as platforms. At least one extra life must be earned to complete the challenge.
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