Harry Hedgehog

Harry Hedgehogs are small, quick-moving blue hedgehogs that appear in Super Mario World 2: Yoshi's Island and its remake Yoshi's Island: Super Mario Advance 3. If Yoshi gets too close to one, the hedgehog swells to a huge size, its spines sticking out. They cannot be eaten while in their defensive position. They usually appear in cavern levels; the 6th level of World 3, The Cave of Harry Hedgehog, is named after this enemy, and prominently features the hedgehogs.

They appear in another level in Yoshi's Island: Super Mario Advance 3, in Go! Go! Morphing!.

Harry Hedgehogs reappear in Yoshi's New Island for the Nintendo 3DS, and their spines are now purple instead of blue.

Trivia

 * Harry Hedgehogs may have been based on Porcupos from Super Mario Bros. 2, as indicated by their Japanese name.
 * Harry Hedgehog's are almost undoubtably a reference to Sonic, since they are blue and move very fast. During the 16-bit era (which happened to be the time that Super Mario World 2: Yoshi's Island was released), Sonic's company of origin, Sega, often mocked the works of Nintendo in various ways (as Nintendo and Sega were business rivals). The Harry Hedgehog may be a retaliation to these mockeries, which may also explain its change in color for its latest appearance.