Dohyo Master
From Sonic Retro
Mecha pig is the boss for Green Hills Zone in Sonic the Hedgehog 2. It bounces around the screen turning into ball form and damaging anything in it's path, similar to Sonic. It's possible to tell that it is about to turn into ball form when it starts stomping and releasing steam from it's snout. There are three directions it can go in, down through the crater in the level, straight across the crater and above the crater. When Mecha pig gets hit enough times it will occasionally roll twice in a row before it uncurls.