From the Super Mario Wiki
Icicle Mites are large icicle-like enemies that appear in the game Wario World.
They resemble large, walking icicles with eyes, and can only hurt Wario if he jumps on their single sharp point. They are weak to Wario's punches and can actually be used as stepping stones; if Wario stunned one and performed a Piledriver on it, the Icicle Mite would embed itself into the ground, where it would remain as a step for Wario to climb up to higher ground. Wario had to move quickly, however, as the Icicle Mite would explode after fifteen seconds of being stuck in the ground.