This Egg Mobile, piloted by Doctor Robotnik, has two rocket-boosters on each side and a giant hammer. It is mostly grey with black and yellow stripes, and red stripes on the rocket-boosters. The hammer is mostly red with yellow and blue stripes.
When the player arrives to wide area, two rocky totem poles raise up underground, which surround the player. Robotnik himself then arrives to fly around the top with his giant hammer. The player is unable to reach the Egg Mobile by jumping normally, so he/she has to think another way to get to the top. Robotnik will hit the tops of each totem pole, and one of four heads will shoot an arrow out of its mouth (sort of resembling the statues that spit energy balls in Labyrinth Zone). Arrows can obviously damage the player while flying and it then gets stuck to the other totem pole in other corner.
Arrows can create climbing pole after hitting the other totem pole, which usually gives the player a chance to get on top of the totem poles, and hit Robotnik freely. When the player climbs once to the arrow, it will be severed by standing on for second. If the player has activated Super Sonic, the player can easily jump to the top of totem pole without using arrows. As with every Egg Mobile in Sonic the Hedgehog 2, Tonkachi Eggman takes eight hits to be defeated, which will make totem poles grumble back to underground and the player is able to move to capsule and end the zone.
In locked-on version of Sonic the Hedgehog 2with Sonic & Knuckles, due the low jump height, Knuckles cannot jump onto the arrow at the top notch of the pole. Knuckles is unable to climb on totem poles and because of this, the boss can be a little challenging.
This boss battle is referenced in Sonic the Hedgehog 4: Episode II in the boss battle of Sylvania Castle Zone. At the start of the battle, the pillars from the original battle appear to trick the player into thinking they are going to fight a remake of the Tonkachi Eggman boss. Instead, the pillars are destroyed by the mechanical tentacles of the Egg Serpentleaf, which turns out to be the real boss of the zone.
When Robotnik hits the top of totem pole, one of faces that shoots arrow is seen to have panic expression due the tremble that the Egg Mobile's hammer causes.