Big Arm is one of Dr. Eggman'sEggmobile mecha and the final boss of Sonic the Hedgehog 3. The Eggmobile has been reinforced with additional plating and enhanced engines. The cockpit is protected by a spiked canopy, preventing Sonic from attacking it from above. Eggman uses the mech's two robotic arms to grab Sonic and then smash him into the ground. The craft's windscreen is its only vulnerable point, meaning Sonic must time his jump attacks precisely to avoid the machine's hands from grabbing him.
In the two-part Sonic the Comic story, Robotnik's Revenge, Dr. Robotnik piloted the Big Arm (referred to as the Squeeze Tag Machine in the comic) as he led an attack on Sonic's secret Freedom Fighter headquarters. The doctor's Badniks dug their way into the base and Robotnik himself battled Sonic. Sonic's attacks were all but useless against the machine, but he was saved by the timely arrival of Knuckles the Echidna, whose powerful punch cracked Robotnik's canopy, allowing Sonic to smash through it and knock the doctor out of the cockpit. Robotnik managed to escape and the Squeeze Tag Machine was buried along with Sonic's base.