Mecha Pig

Mecha Pig, known in Japan as Mecha Buta (メカブタ), is the boss of the Green Hills Zone in Sonic the Hedgehog 2 for the Game Gear and Master System. It is a robotic pig modelled after a sumo wrestler, with the ability to curl into a ball (imitating Sonic's Spin Attack) and roll or float from one side of the screen to the other. While rolled up, he is invulnerable to Sonic's attacks.

The boss battle takes place on a grassy field with a dip in the middle. Mecha Pig will stand on either side of the dip and perform a sumo stomp and snort steam, after which it will curl into a ball. It will then move across the dip, either rolling down along the grass, or floating straight across the middle, or moving across the top of the screen in an arc. On the other side, Mecha Pig will uncurl to perform another sumo stomp, and this is when Sonic must attack.

After being hit a certain number of times, Mecha Pig will sometimes roll across the screen twice before uncurling.