He first appears in the game Sonic & Knuckles .
Two robotic versions of Knuckles have appeared ( similar to Metal Sonic ) ; Metal Knuckles in Sonic R , as an unlockable character , and Mecha Knuckles in Sonic Advance , as a boss . The robotic Knuckles in Sonic Advance looks exactly like Knuckles , only with a pinker hue and yellow gloves at first , and has virtually every move Knuckles has .