Gamma was created as one of the first of Dr. Eggman's E-100 Series, along with Beta, Delta and Epsilon. After succeeding in capturing Froggy while the others failed, he was ordered to take away Lily, a little blue bird. Amy refused to hand her over, and the robot was stunned. He realized that he was just Dr. Eggman's tool. He rescued Amy and Lily, becoming their friend. Under Eggman's control, he attacked Sonic who nearly destroyed him, but was stopped by Amy. Afterwards, Gamma deleted the image of Eggman in his head. He then reprogrammed his brothers.
After reprogramming Zeta on the Egg Carrier, Beta attacked him and they engaged in combat. Gamma eventually removed the Flickies inside them and they collapsed, "dying". Their hands were then put together in front of Amy (Japanese version only).
Gamma has a similar personality to his game counterpart, though he was cast with being slightly more emotional and was capable of being frightened and disturbed even before he met Amy, even able to exhibit organic like exclamations such as groaning and at one point even producing a forlorn facial expression (also seen on Bocoe, Decoe and Bokkun). It still portrays Gamma's naivety towards good and evil however, perhaps best exhibited when he ignored Big and Chris trespassing on the Egg Carrier.
- In the English version, Gamma's voice is high-pitched instead of deep like Sonic Adventure.
- Unlike in Sonic Adventure, Amy sees Gamma destroyed.
|Heroes||Sonic | Tails | Amy | Knuckles | Cream | Cheese | Christopher Thorndyke | Big | Tikal | Vector | Espio | Charmy | Cosmo | Chuck Thorndyke | Helen | Danny | Frances | Nelson Thorndyke | Lindsey Thorndyke | Sam Speed | Ella | Mr. Tanaka | Mr. Stewart | Topaz | Hawk | Froggy | Emerl|
|Neutral/Anti-hero||Shadow | Rouge | Chaos | Gamma | ZERO | Beta | Delta | Epsilon | Zeta | Pachacamac|
|Villains||Eggman | Decoe | Bocoe | Bokkun | King Boom Boo | Bio Lizard | Dark Oak | Red Pine | Yellow Zelkova | Pale Bayleaf | Black Narcissus|
|Groups||Eggman Empire | E-Series | Chao | S-Team | G.U.N. | Chaotix | Cosmo's species | Metarex|
|Miscellaneous||Vanilla | President | Christina Cooper | Jerome Wise | Scarlet Garcia | Captain Westwood | Gerald Robotnik | Maria | Lily | Doctor Kai Narasu | Hector Dragg | Li Yan | Howard Watcher | Card Passer | Albert Butler | Elmer Johnson | Principal | Mayor | Next | Molly | Leon | Earthia | Galaxina | Landar | Daisy | Starla|