The E-100 Series is a group that appears in the anime series Sonic X. They were developed by Dr. Eggman as a line of combat robots and the next stage in his E-Series. They were created to aid in the building of the Eggman Empire using the being known as Chaos, but they were thrown aside and later disabled or destroyed before fulfilling their purpose.
After discovering an incredible being known as Chaos, Dr. Eggman planned to bring it to full power to destroy Station Square and build the Eggman Empire on the ruins of the city. To that end, he invented six new robots known as the E-100 Series; E-100 Alpha (or ZERO), E-101 Beta, E-102 Gamma, E-103 Delta, E-104 Epsilon and E-105 Zeta. Beta, Gamma, Delta and Epsilon were powered by animals and initial tests proved promising with their fine marksmanship on the shooting range and unflinching obedience. ZERO was the first one to see action in the field, being sent after a bird who was in possession of a Chaos Emerald that had escaped from the Egg Carrier. ZERO traveled down to Station Square and after finding the bird (who had been named "Lily") in Amy Rose's care, kidnapped them both, and flew back to the Egg Carrier moments before Sonic could arrive to save them.
Shortly afterward, Beta, Gamma, Delta and Epsilon were given the task of finding a frog that was in possession of both a Chaos Emerald and Chaos' tail. All four robots managed to find a frog, but Gamma was the one to find the right frog, having stolen him from Big the Cat and Christopher Thorndyke who were also searching nearby. The four robots returned to the Egg Carrier to present their findings, leading to Eggman becoming incredibly angry with their apparent incapability and stupidity. When he saw that Gamma had retrieved the correct frog, he dismissed the others as useless and teleported them away, sending Beta for upgrades to become E-101 "Kai", Delta to be tied to a rock pillar in Windy Valley, and Epsilon left in a cave. This event marked a change in direction for the E-100 Series. Gamma was next ordered to retrieve Lily from Amy Rose in her cell, but was so distracted by the events that had taken place, and after suddenly seeing a vision of Lily, he accidentally walked into a room where Beta was being upgraded, but was reminded by Eggman of his orders and headed again for Amy's cell. Gamma threatened the pink hedgehog at gun point, but she staunchly refused and made Gamma question its motives. At this point, Lily flew through the cell's bars, looking Gamma in the eye and the robot clutched its head in pain before telling Amy to flee and blowing open the cell. Gamma then looked back at Lily who had still not left and told her directly to leave. Before they left, Amy told Gamma that the next time they meet they would be friends and Gamma, contemplating this thought, returns to serving Eggman whilst still thinking about Lily. Gamma was soon after called upon by Eggman to head to rear deck of the Egg Carrier and was ordered to shoot Sonic. Amy tried to break up the fight, telling Sonic that Gamma was good. The blue hedgehog initially hesitated, but the robot did not hold back in its attack and Sonic quickly knocked Gamma to the ground, disabling it. Before he could finish Gamma off however, Amy stopped him. Amy then managed to re-activate Gamma and told the robot that it did not have to listen to Eggman any more and should flee as well.
After flying off the Egg Carrier and landing in a mountainous region, Gamma thought over all that had happened and deleted Eggman's designation as its master and went to free Beta, Delta and Epsilon, having visions of birds. Gamma first released Delta, erasing Eggman as its master and shutting the robot down, releasing the rabbit animal trapped inside. Gamma then did the same with Epsilon, making sure to destroy the statue of Eggman before he left to find Beta and Zeta on the Egg Carrier. Along with them was ZERO, who had been stranded in the Egg Carrier with Decoe and Bocoe. The three robot minions quickly discovered Amy and attempted to capture her, only for Amy to outwit Decoe and Bocoe and knock ZERO aside with her Piko Piko Hammer. Meanwhile, Gamma had successfully disabled Zeta when Beta, now upgraded to E-101 "Kai," attacked Gamma. The rebellious robot tried to reason with Beta, but his obedience to Eggman would not be broken. Amy Rose again tried to break up Gamma's fight, but the two robots struck each other down, arms entwined as their metal bodies went down in flames. Following their destruction, the birds powering Gamma and Beta were released, revealing them to be Lily's siblings.
- In the original Sonic Adventure and Sonic Adventure DX: Director's Cut games, E-105 Zeta was initially built as a bipedal robot just like its brothers and was upgraded to become part of the Egg Carrier, similar to how Beta was upgraded. In Sonic X, Beta takes Zeta's place until Zeta is seen for the first and only time in "Revenge of the Robot".
- In the episode "Pure Chaos", the animals shown placed in Beta, Gamma, Delta and Epsilon are inconsistent with what we are shown in "Revenge of the Robot." Beta is given an unknown creature, Gamma is given a rabbit, Delta is given the pink bird, and Epsilon is given the cream bird. Later on in "Revenge of the Robot", Beta has the cream bird, Gamma has the pink bird, Delta has the rabbit and Epsilon's is never seen.
- In the original Sonic Adventure and Sonic Adventure DX: Director's Cut games, all the E-100 Series save for ZERO were powered by birds.
- Yoshimura, Kiyoko (18 September 2004). "Pure Chaos". Sonic X. Season 2. Episode 27.
- Yoshimura, Kiyoko (25 September 2004). "A Chaotic Day". Sonic X. Season 2. Episode 28.
- Houjou, Chinatsu (2 October 2004). "A Robot Rebels". Sonic X. Season 2. Episode 29.
- Shiraishi, Masahiko (16 October 2004). "Revenge of the Robot". Sonic X. Season 2. Episode 31.
- Urasawa, Yoshio (9 October 2004). "Heads Up, Tails!". Sonic X. Season 2. Episode 30.