E-105 Zeta

E-105 Zeta is initially a silver and purple robot identical to E-102 Gamma in every way (besides color), though it is later altered and reconstructed as a considerably larger stationary defense unit built into the core of the Egg Carrier, equipped with seven advanced missile launchers. Despite being better, Gamma fought and defeated Zeta in the Hot Shelter onboard the Egg Carrier, releasing the trapped animal inside after Zeta's head exploded. A Dreamcast console is included in Zeta's exterior design, inserted by Sonic Team as an Easter Egg. This is in all the Dreamcast, Gamecube, and PC versions.

In Sonic X, E-101 Beta replaced much of Zeta's role, so much that in fact, Zeta only appears on the show in episode 31, "Revenge of the Robot". This is when Gamma comes to the Hot Shelter to destroy him.

Post Eggman
E-105 Zeta was banished by Dr.Eggman for finding the wrong frog when he was searching for Froggy (since froggy accidentally swallowed Chaos's tail. He is then altered to a different model and later destroyed.