Charge Master, known as Inobuta Mecha (イノブタメカ) in Japan, is the third boss of the 8-bit versions of Sonic the Hedgehog 2, fought at the end of Gimmick Mt. Zone. "Inobuta" is Japanese word for a pig-wild boar hybrid, which is what the boss resembles.
This metal-spiked kill-hog crashes from one end of the screen to another, dislodging heavy rocks from the ceiling when it impacts. These are deadly in and of themselves, never mind the crazed robot running around beneath them; however, the prickly pig robot hits the side of the screen so hard that the machine stuns itself when it collides with the side of the arena, retracting its spikes and giving Sonic a short window of opportunity to do some damage. Curiously, if Sonic hits the boar fast enough when it is stunned, no rocks will be dislodged from the ceiling.
After hitting it eight times, the robot will be destroyed, allowing Sonic to break the Prison Egg and proceed to Scrambled Egg Zone.