The new animated Disney+ series Star Wars: The Bad Batch tells the story of an eclectic group of clones, each with their own special abilities. The crew of Clone Force 99 (otherwise known as The Bad Batch) — which includes clones named Hunter, Tech, Crosshair, and Wrecker — was most recently seen during Star Wars: The Clone Wars, an animated series that ran for seven seasons. The four-episode arc that introduced the team of clones with genetically enhanced abilities also told the story of how they acquired their fifth member, a clone named Echo.
Echo was originally a regular clone who was part of the Domino Squad in the Clone Army, before eventually being promoted to the position of ARC trooper. After he went missing during an attempt to free detainees from a Separatist prison, Echo was presumed dead, when in actuality he was being held captive by the Separatists. But after his old friend Captain Rex had a feeling that the Separatists were somehow using intel from Echo to gain an advantage in the Clone Wars, Rex recruited Clone Force 99 to help him infiltrate the Separatists’ cyber center.
After Bad Batch member Tech tracked the Separatists’ algorithm, Rex realized Echo was still alive and led Clone Force 99 and Anakin Skywalker on an unauthorized mission to rescue Echo. When they found Echo, he was barely recognizable — his entire body had been implanted with cybernetics in order for the Separatists to mine him for information on the Republic, turning him into a being that was half droid and half clone. These modifications also gave Echo the ability to interface with secure computer systems.
After he was rescued from the Separatists by Captain Rex and Clone Force 99, Echo’s new emotionless droid-like demeanor led some of the clone troopers that used to fight alongside him to doubt his loyalties. Although Echo proved his loyalty to the Republic during a stealth mission, he grew to feel more comfortable with the Clone Force 99 than with the Clone Army, which is what led him to decide to leave his longtime friend Captain Rex and join up with the rest of The Bad Batch.