Echo debuts alongside Fives in "Rookies" (2008) and is apparently killed in the Citadel arc. He is voiced by Dee Bradley Baker.
The series brings him back in its seventh season as a Techno Union asset: kept alive, stripped of most of his body, and wired into a Separatist strategic computer whose predictive accuracy the Republic could not explain. The Republic's losses were being calculated by one of its own men.
Recovered, he joins Clone Force 99 and carries into The Bad Batch as the squad's conscience — the member who most often argues that the other clones are still worth going back for. He is also the only one of them who was a regular trooper first, which the series uses to keep the squad honest about what they were built to think of everyone else.