Hard-Boiled Heavies

"A powerful robot army built by Dr. Eggman. Loyal to his orders, the Heavies successfully retrieved the mysterious gemstone, but its power seem to have loosened a few of their screws."

- The Sonic Mania manual description of The Heavies.

The Hard-Boiled Heavies (ハードボイルドヘビーズHādoboirudohebīzu?) HBH for short, are a group of elite robots under the command of Dr. Eggman.

After getting struck by the power of the Phantom Ruby, they became surprisingly intelligent and strong, and went over the standards of what Eggman thought they were capable of.

They were created by Christian Whitehead, and their theme song was made by Tee Lopes and Falk Au Yeong.

Creation
Interestingly enough, when they were created by Christian Whitehead, he imagined that Dr. Eggman got depression after the events of Sonic the Hedgehog 3 & Knuckles and wouldn't even try to go after Sonic anymore. And would just chill at home. And that his abandoned robots would go mad thinking of this, and that's how they were created.

Beginnings
The Hard-Boiled Heavies were at first five elite robots that serve Dr. Eggman, being elite members of his robot army, they did the hardest missions for him and were one of his best robots, Eggman read about a powerful energy source that resided on Angel Island. Obviously the Hard-Boiled Heavies went to catch this, when they were there, they took it, but became even more powerful forms, the robots went insane after this and became evil.