Artwork of Tunnelbot taken from the US manual of Sonic the Hedgehog 3.
Marble Garden Zone Act 1
Long bot with two drill engines, which it uses to drill into ceilings and causing terrain changes. Takes six hits to defeat it.
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 him occasional times in the Zone until Tunnelbot appears as mid-boss in the end of the act. To defeat Tunnelbot, the player has to hit it six times to destroy it.
Tunnelbot is a long bot created by Doctor Eggman with two drills on top to dig through the ruins of Marble Garden Zone's fortresses. Drill engines are inside two yellow and red colored covers with blue lines on each one. The bot itself between the large drills only has a flat head with a cyan-colored eye.
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 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. 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 jump off the first seen long pillar to the left side.
Once the player reaches to the end of the act, Tunnelbot will appear and immediately burrow into the ceiling. The battle takes place inside the temple, where rocks will fall from ceiling to the ground, with 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, Tunnelbot itself will fall down, trying to injure the player. This is the good time to attack it. Tunnelbot will eventually rise up again and repeat the same pattern again, while it can drop himself from different places. After it has received six hits, Tunnelbot will be destroyed. When the signpost falls down, one Thunder 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 locked-on version of Sonic the Hedgehog 3 & Knuckles, Knuckles confronts Tunnelbot occasionally in the Zone and at the end of first act normally. However, as Knuckles has low jump height, the battle is more challenging as Tunnelbot will not strike the ground like during its fight with Sonic/Tails. After Tunnelbot drills into ceiling, a large rotating spiked pillar will rise from the corner and start moving to the another corner after Tunnelbot drills into ceiling. It can help Knuckles reach into Tunnelbot, but the player has to look out for spikes on the pillar while it moves. Dealing six hits normally will destroy Tunnelbot.
Apperances in other media
Sonic the Comic
In the British Publication of 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 other's by Knuckles' powerful punch.
Tunnebot makes small cameo appearance along other Badniks from Sonic the Hedgehog 3 in one panel of French Sonic Adventures comic, as Robotnik is sending all units after Sonic and Tails.
- 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.
- Another robot called Lava Drill appears in Lava Reef Zone from Sonic & Knuckles, but had some differences.
- Tunnelbot is one of only sub-bosses featured in the US manual of Sonic the Hedgehog 3.