Mr. Delta is a criminal genius who, along with Ms. Alpha, Mr. Beta and Mr. Gamma, attempted to steal the treasure of the Floating Island, and a villain in the Sonic Hedgehog comic book series. He is a male, anthropomorphic creature, although his exact species is unclear. He is a member of the criminal gang led by Ms. Alpha, and along with Mr. Gamma, acts as the brains of the outfit.
The gang attempted to steal the Chaos Emeralds. They came very close to succeeding, repeatedly outwitting the Island's Guardian, Knuckles The Echidna with the assistance of numerous gadgets. However, their plan was eventually thwarted by Porker Lewis.
He first appeared in Sonic The Hedgehog #135.
Posing as new recruit, the gang infiltrate a D.R.A.T mission to steal the Chaos Emeralds under the pretense that they have the wherewithal to neutralize the Floating Island's Guardian Robots. However, the gang soon betray the D.R.A.T. operatives, leaving them to be captured by the Robots. Pursued by Knuckles, Mr Delta's comrade Mr Beta confronts the echidna, Mr Delta blinds Knuckles with a laser-like weapon.
Mr Beta throws the blinded Knuckles off the Floating Island, and the gang go in search of the Emerald Chambers, only to be confronted by the Guardian Robots. As Mr Beta holds them off, Mr Delta and Mr Gamma work frantically to configure the Chameleon Circuits, a device which will render the gang invisible to the Robots' sensors. They eventually succeed, and proceed into the network of tunnels leading to the Emerald Chamber where they're confronted once again by Knuckles. As the echidna dealt with Mr Beta, he was ambushed from behind by Mr Gamma, who successfully fixed a shock-collar around Knuckles' neck at Ms Alpha's suggestion. Ms Alpha then produces a remote, electrocuting the echidna.
Trusting the collared Knuckles would now give up, the crew proceeded to the Emerald Chamber, but the persistent Guardian again gave chase. Tackling Mr Beta to the floor, Knuckles threw a stone, knocking the collar's remote out of Ms Alpha's hand. As the echidna attacked Mr Gamma and Mr Delta, Ms Alpha retrieves the remote. However, it was then snatched out of her hand by a Guardian Robot. Shocked by the apparent failure of their gadget to neutralize the Robots, Ms Alpha and co. submit, and are escorted away by the Robots.
It is later revealed that the Robots were in fact being piloted manually by Porker Lewis.
- Mr Delta shares his name with E-103 Delta, a robot from Sonic Adventure.