Egg Mobile-D, short for Egg Mobile Drill Machine-shiyou (エッグモービル・ドリルマシン仕様,Eggumōbiru Dorirumashin-shiyō?) and also known as Drill Eggman (ドリルエッグマン,Doriruegguman?), is the first boss in Sonic the Hedgehog 2. It first appears at the end of Emerald Hill Zone Act 2, but also also appeared as one of the mid-bosses in X-Zone of Sonic Advance. In both games, it is piloted by Dr. Eggman.
Egg Mobile-D is a predominantly red and grey armoured dune buggy-like vehicle that runs on four wheel drive. Its main features include a large spinning drill on the front end of the machine, sharpened spikes on its hubcaps, autopilot, effective off-road capabilities, and the ability for its chassis to link with the Egg Mobile to provide both a cockpit and a makeshift escape pod in case the main chassis is destroyed. The drill is capable of functioning as a long-ranged but somewhat slow projectile weapon, as it can be launched from the front end towards the player. The front of the vehicle bears resemblance to a mole.
Sonic the Hedgehog 2
Egg Mobile-D is known to be first boss featured at Emerald Hill Zone Act 2 in Sonic the Hedgehog 2 under the name Drill Eggman. The battle takes place on arena with palm trees and slightly uneven terrain. At the beginning of the boss fight, Dr. Robotnik arrives in his Egg Mobile (which unusually flies by means of helicopter-style rotor blades), which attaches to the drill vehicle. Dr. Robotnik then proceeds to drive the drill car back and forth across the screen.
Dr. Robotnik is vulnerable to a simple Spin Attack on his head. The player is able to hit from behind, while the player has to watch out the drill part. After being hit seven times, the doctor laughs and shoots the drill-bit straight off the car. One final hit is required to destroy the machine, after which the scientist detaches his Egg Mobile from the vehicle and flies away. The player can then open the zone's capsule and complete the level.
In the version of Sonic the Hedgehog 2 from the Sonic Cafe mobile phone service, Drill Eggman is slightly bulkier and has a little more armor, making the hitbox of vehicle smaller to attack.
After many years, this machine appears again in Sonic Advance as one of recycled bosses featured at X-Zone. The Egg Mobile-D is the second boss of X-Zone and is once again piloted by Dr. Eggman.
However there are slight differences now. In the beginning of the fight, Eggman is already seen in the Egg Mobile-D, when it arrives to the battle arena. The arena itself is completely flat, which makes the fight even easier. This version takes only four hits to be destroyed, while like in Sonic the Hedgehog 2, it shoots its drill part towards the player just before the final blow. After destroying the Egg Mobile-D completely, Dr. Eggman flees, allowing the player to progress further in the X-Zone and to the the latest weapon, that Eggman has prepared for the last.
Egg Mobile-D was originally going to be Eggman's racing vehicle in Sonic & Sega All-Stars Racing, as it is shown to be somewhat smaller in early concept art. In the finished product however, Eggman's racing car became Egg Monster.
In Sonic Jam compilation, Drill Eggman is one of three bosses that the player will encounter in the easy mode of Sonic the Hedgehog 2. While having an identical attack pattern, it only takes three hits to defeat it.