This article's name is conjectural. Although this article is based on official information, the actual name of the article's subject is pure conjecture.
Knuckles facing off against the Tunnelbot in Lava Reef Zone Act 1.
Tunnelbot is a robot built by  Dr. Robotnik, that briefly appears at Lava Reef Zone Act 1 in . The robot seems to be a larger variation of the first Sonic & Knuckles Tunnelbot from Marble Garden Zone, with four drill attachments.
The Tunnelbot appears three times in Lava Reef Zone, once in
Sonic's story and twice in Knuckles' story (depending on if the player takes the upper pathway behind the robot). In both stories, when the player faces it in the open area, the robot is about to start the drilling process, which makes the ground below collapse. In Sonic's story, the robot falls into the lava pool, and in Knuckles' story, it attempts the same process but stays on the edge of the upper platform where it remains intact.
Sonic the Hedgehog 3 & Knuckles
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