ZERO

ZERO, also known as E-100α or E-100 Alpha (Ｅ－１００ “アルファ”) is character in the Sonic the Hedgehog series who first appeared in Sonic Adventure. It is a large, red-eyed, floating green robot that resembles a trash can with large arms that tries to recover Chaos Emeralds. During its mission, ZERO relentlessly pursued Amy Rose for the Chaos Emerald she unknowingly had until it had the bad luck to be on the receiving end of Amy's hammer.

Appearance
Unlike the E-100 Series robots, it does not have "E-100" on its body, but instead it has "E" on both sides of its body. Also, the headlight on ZERO is on its shoulder, in contrast to the E-100 Series robots in which it is on their mid-section.

History
In Sonic Adventure, ZERO made its 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 it went back to the Egg Carrier, it 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 with an extending punch. Amy, thinking that ZERO had killed her companion, became furious and attacked ZERO - finally destroying it by knocking it into an electric fence, scrambling its circuits, before smashing the vulnerable circuitry in its head with her hammer, causing him to explode.

Personality
ZERO pursues its target 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. When pushed to the brink however, it becomes much more aggressive.

Powers and abilities
ZERO differed greatly from the other E-100 robots as it lacked a projectile weapon of any sort, mainly relying on its 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 also seems to possess an "overdrive" mode after taking a certain amount of damage, where steam begins bellowing from its smokestack-like head, rendering it invulnerable to any sort of attack.

Sonic Advance 2
ZERO makes a brief appearance in Sonic Advance 2, chasing the player around the Special Stages of the game. In this appearance, it is known as the Robot Guard (ガードロボ), but otherwise looks identical to its previous appearance. If it hits the player, they lose ten rings.

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

Boss guide
Amy ends her adventure by battling Zero on the Egg Carrier's deck. It's easier than running from Zero through the Adventure Stages; all Amy has to do is knock Zero against the electric ropes that encircle the ring. When Amy swats Zero into the hot wires, its body gets an unhealthy jolt, and the top of its green noggin flips back to reveal a big, blue button. Hit that button four times, and Zero goes boom. Hammer Zero into the electrical ropes, and it crackles with an overload of juice. When Zero flips its lid, jump up and Hammer the blue button under it. Zero attacks with shock waves; keep some distance between Zero and Amy to hop over them. When Zero's almost finished, it sends an electric "jump rope" after Amy, which she must skip to survive. Run along in the same direction that the rope is turning as you jump to easily avoid it.

Sonic X
ZERO also appeared in the anime series Sonic X, in the Chaos Saga. His role in the series mirrors to that in Sonic Adventure.

Trivia

 * Alpha is the first letter of the Greek alphabet. Zero (AKA Alpha) is said to technically be the direct predecessor of the E-100 Series robots.
 * The first letter of the Greek alphabet is sequenced as 0. Perhaps that is why ZERO is occasionally known as Alpha.
 * ZERO is not powered by an animal like its immediate successors, as nothing is seen escaping from its body after its destruction.
 * Although it is not called an E-Series robot in the games, it was given a similar codename on the Sonic Adventure website accessed via Dreamcast.
 * Despite its name in supplemental sources, Eggman apparently does not consider ZERO to be a part of the E-100 Series, as he calls E-102 Gamma his second model.
 * The reason for this may be that ZERO is the last of the pre E-100 Series robots.
 * ZERO, E-105 Zeta (the second form), E-121 Phi and E-123 Omega are the only earlier E-Series robots that do not follow the same basic design as E-101 Beta.
 * As a villain, ZERO has traits common to the Strong Silent Types of "slasher" movies in that it is big, slow, strong, and cannot be hurt or killed under normal circumstances.
 * In the early Japanese Sonic Adventure website, ZERO is also dubbed the Prototype of the "Eggrobo" E-Series (エッグロボＥシリーズの試作機). It is uncertain if this is supposed to be meaning behind the "E" in E-Series, if it was actually intended to be a throwback to Eggrobo, or if this was outdated information by the game's final release.
 * ZERO is sometimes known among fans as "The Chase Master" due to the name of its song on the soundtrack.