ZERO

E-100 Alpha, better known as ZERO (sometimes with the added title The Chase Master after the name of his song on the soundtrack) is a large red-eyed floating green robot that resembles a trash can with large arms that tries to recover Chaos Emeralds and appeared in Sonic Adventure. Although he is called an E-Series robot in the games or Sonic X, he was listed as "E-100 Alpha" on the Sonic Adventure website accessed via Dreamcast. Unlike the other E-100 series robots it does not have "E-100" on its body, but instead it has "E" on both sides of his body. Also, the headlight on ZERO is on his shoulder, in contrast to the other E-100's in which it is on their mid-section. ZERO is also not powered by an animal like the other E-100 robots, as nothing is seen escaping from its body after its destruction.

ZERO differed greatly from the other E-100 robots as he lacked a projectile weapon of any sort, mainly relying on his extending fists to attack its foes. It also possessed impressive strength, able to smash through walls in pursuit of Amy. It also had strong defensive strength, as Amy could only inflict damage by electrocuting it. It pursued its prey with a single-minded tenacity, even after the Flicky's Chaos Emerald had been removed. This also made it possible to trick it, as Amy could hide beneath barrels or around obstacles to elude it.

In Sonic Adventure, ZERO made his debut by chasing a blue Flicky in the possession of a Chaos Emerald that has taken refuge with Amy Rose. ZERO chased Amy around Station Square, Twinkle Park, the Egg Carrier, Hot Shelter, and finally, the Final Egg base in the Mystic Ruins.

When he went back to the Egg Carrier, he saw Amy and the Flicky with the bird's relatives, who were inside E-101 Beta and E-102 Gamma. ZERO then attacked and knocked out the small Flicky. Amy who was furious at him and thinking the Flicky was dead due to the attack, attacked ZERO and finally destroyed him after smashing his head with her hammer, knocking him into an electric fence that fried his circuits. ZERO also seems to make a brief appearance in Sonic Advance 2, chasing you around the pseudo 3D special stage. The manual however, describes him as Dr. Eggman's Guard Robot but he looks exactly the same. If he hits you, you lose 10 rings.

ZERO appeared in Sonic Rivals 2 as collectible card No. 81. It was unlocked by obtaining the high score in Zone 6 Act 3.

Trivia

 * Alpha is the first letter of the Greek alphabet. Zero, a.k.a. Alpha, is the first of the E-100 Series robots.
 * Alpha, Zeta (in his second form), Phi and Omega are the only known E-100 robots that aren't a complete copy of Gamma.
 * The first letter of the Greek Alphabet is sequenced as 0. Perhaps that is how Alpha is commonly known as ZERO.