In Sonic Adventure and Sonic X, Zero (E-100 Alpha) is an E-Series robot created by Dr. Eggman to capture the blue bird Amy Rose travels with. Throughout the game, he would always attempt to stop the player and get in the players way. Zero is defeated by Amy aboard the sunken Egg Carrier.
In the Sonic Advance games
In the Sonic Advance games (more specifically Sonic Advance 2), Zero is an obstacle in the special stages to prevent you from collecting the amount of rings you need to collect the Chaos Emerald. This is the final game he's appeared in aside from cameos in other game such as Sonic Rivals.
- Even though Eggman already has the Chaos Emerald from the blue bird Amy dubbed as "Birdy," Zero still chases after Amy throughout her story.