Spiked ? Block

'''Spiked ? Blocks' are a type of block first found in New Super Mario Bros.'' This block is similar to a regular ? Block; however, it has spikes at the top. It also spins around, requiring the player to mind their timing to avoid getting hurt. Hitting or ground-pounding the non-spiked side will turn the block into an Empty Block.

The blocks appear only in World 6-3, where four of them are seen, three of which contain power-ups.

Trivia

 * If Mario ground-pounds the block right as it begins to spin around, he will be flung away by the spin.