Gapsule

The Gapsule is a mini-boss from the game Sonic and Knuckles, and it's locked-on form Sonic 3 and Knuckles. The boss takes on the appearance of a Capsule, however one the button on the top is presses, two arms with spike-balls appear, as well as a face. To defeat the boss, you must stand on the button long anough to make the Gapsule to try crush you with one of his spike-ball arms. If you jump out of the way quickly, Gapsule will hit himself instead, dealing a hit in damage. Repeat this 5 times to defeat the boss.