The Tunnelbot (ガキーン Gakīn?) is a sub-boss that appears in Sonic the Hedgehog 3. In Marble Garden Zone Act 1, the player encounters the Tunnelbot occasionally throughout the Zone until it appears as the sub-boss at the end of the act. To defeat the Tunnelbot, the player must hit it six times to destroy it.
The Tunnelbot is a wide robot created by Dr. Robotnik with two drills on top, used to dig through the ruins of Marble Garden Zone's temples. Drill engines are inside two yellow and red colored covers with blue lines on each. The robot itself (sitting in between the large drills) only has a flat head with a cyan-colored eye.
The Tunnelbot appears in several places of Marble Garden Zone Act 1. It will wait for the player to arrive and will then drill into the ceiling, sometimes causing changes in the terrain. The player can jump at the Tunnelbot to damage it, but it cannot be defeated in the short time that it is vulnerable to damage, and the damage dealt has no effect on the boss battle. The Tunnelbot can eventually be found after the player takes the first alternate pathway or lower pathway through the temple section of the act. It can later be found again in another temple section, if the player goes around the downward guiding Shuttle loop and jumps off the first seen long pillar to the left.
Once the player reaches the end of the act, the Tunnelbot will appear and immediately burrow into the ceiling. The battle takes place inside the temple, where rocks will fall from the ceiling to the ground, some of the rocks being spiky stalactites capable of hurting the player upon contact. However, if the player is equipped with a shield, the stalactites can be deflected. A few seconds later, the Tunnelbot itself will emerge downward from the ceiling, trying to injure the player. This is the good time to attack it. The Tunnelbot will eventually rise up again and use the same pattern again, dropping out from different places each time. After it has received six hits, the Tunnelbot will be destroyed. When the signpost falls down, one Lightning Shield monitor can be pop up from the left-side mound while Super Ring and Flame Shield monitors pop up from the right-side mound.
In the Sonic the Hedgehog 3 & Knuckles lock-on, Knuckles confronts the Tunnelbot occasionally in the Zone and at the end of first act normally. However, as Knuckles has a low jumping height, the battle is more challenging, as upon exiting the ceiling the Tunnelbot will stop descending at a high position that is out of reach of Knuckles' jump (as opposed to moving all the way down to the ground in the battle with Sonic/Tails). As the Tunnelbot drills into the ceiling, a large, rotating spiked pillar will rise from the corner and start moving to the other side, which can indicate where Tunnelbot will exit out of after drilling in the ceiling. It can help Knuckles reach the Tunnelbot, but the player must look out for spikes on the pillar while it moves. Dealing six hits normally will destroy the Tunnelbot.
In other media
Sonic the Comic
In Sonic the Comic, Tunnelbots appeared following Doctor Robotnik's discovery of the Floating Island. However, they are standard members of his Badnik army, and there is no suggestion of their being any different from any other Badniks.
Tunnelbots first appeared as part of the force that attacked Sonic's Secret Underground Base, forcing the Freedom Fighters to abandon it. A Tunnelbot later appeared in the service of Robotnik's minions, the Marxio Brothers, guarding the Carnival Night Zone. It was among several Badniks that the Marxios used to attack Knuckles the Echidna, but it was destroyed along with the others by Knuckles' powerful punch.
Tunnebot makes small cameo appearance alongside other Badniks from Sonic the Hedgehog 3 in one panel of the French Sonic Adventures comic, as Robotnik is sending all units after Sonic and Tails.
- The Tunnelbot's fight is loosely similar to the Drill Eggman II's fight at Mystic Cave Zone in Sonic the Hedgehog 2, as both vehicles can drop spiky rocks from the ceilings.
- A very similar robot briefly appears in Lava Reef Zone of Sonic & Knuckles.
- The Tunnelbot is the only sub-boss featured in the US manual of Sonic the Hedgehog 3.