— Eggman, during the slam attack
The Egg Breaker is a mech with an open cockpit that Dr. Eggman sits in. It somewhat resembles the Egg Emperor from Sonic Heroes, except it bears a red and blue paint scheme instead of gold, and its right hand is a giant spiked ball that it can throw, which is used to try to crush Shadow and create shock-waves. On average it takes 23 shots from a normal gun to defeat.
It can jump to create a shock-wave, spin around with its spikeball, throw its spikeball, fire balls around it, and fire lasers. It also has the ability to leap considerable distances, fire horizontal arrays of bombs, shoot laser beams with its eyes and throw its spiked ball (it quickly generates a new one).
Egg Breaker appears as a boss after the Cryptic Castle stage after any mission is completed. Amy Rose is the player's partner. The battle takes place on a circular platform. There is a trail of rings around the platform and ghosts sit at the very edge. During this battle, Eggman will attempt to smash the player shouting "Lights out!" as his main attack. If the player gets too far away from him, he will fire his hammer at them. The Egg Breaker's third attack is the deadliest. It will spin around and around as it swings its hammer, making it invulnerable to all attacks.
Egg Breaker also appears as a boss after the Mad Matrix stage after any mission is completed. Espio the Chameleon is the player's partner. The battle takes place inside a cylinder shaped room with a trail of Rings going around it. There are floating cubes above that have Egg Pawns and jars of Rings on them. The only way to get up there is by using an ascending bar of light. Eggman attacks similar to the way he did at Cryptic Castle. But this time he'll spin and send out bombs with his face on them while shouting "You know what they say, the more the merrier!".
Egg Breaker makes its final appearance as a boss after the Iron Jungle stage after any mission is completed. E-123 Omega is the player's partner. The battle takes place inside Eggman's base; another circular room. There is a platform in the center. Near the outside of the circle, there are two turrets and two rockets. This Egg Breaker battle is vastly different from the previous two. Eggman doesn't engage in hand-to-hand combat with the player as he did before. Instead, he sits on the center platform and fires lasers from the Egg Breaker's eyes. The easiest way to defeat it is by using the turrets. However, the Egg Breaker's lasers will eventually destroy the turret. Another method of attack is using the rockets to get to the Egg Breaker's level. After it gets down to half HP, the Egg Breaker will jump off the platform. It will still fire lasers rather than attacking directly, unless the player gets too close. Despite all of this, it is considered to be the easiest of the Egg Breaker battles because of the absences of the close range attacks.
- The Mad Matrix version of this boss fight is considered to be the most difficult of the Egg Breaker's boss battles because the most useful weapons are kept up on top of the blocks.
- In addition, this version is known for carrying Eggman's infamous one-liner, "You know what they say, the more the merrier!", which he says every time he uses the bomb attack. Many players have found this quote very annoying due to Eggman's repetitive usage of it. This makes the Egg Breaker one of six of Eggman's machines to have an infamous quote tied to it. The others are the Egg Viper and the Egg Walker from Sonic Adventure ("Get a load of this!") the Egg Emperor from Sonic Heroes ("Take this!"), the Egg Devil Ray from Sonic Unleashed (Wii/PS2 version only) ("You little! You little!") and the Egg Dragoon from Sonic Generations ("Time for a change of pace!").
- Despite the fact that destroying Egg Pawns in this boss fills the Hero Gauge, Amy and Espio will often tell Shadow to stop attacking them. Omega is the only ally to this boss that encourages Shadow to destroy them.