After Sonic the Hedgehog thwarted Dr. Eggman in their last encounter, the doctor disappeared while his Caterkillers and the rest of his Badnik army remained. Without a leader however, the Caterkillers were directionless and no longer a unified threat. Even so, they would still randomly attack anyone they came across (although such incidents were more accidental than aggression-based).
Basically, the Caterkillers are mindless and silent drones programmed to follow their leader's every command. As such, when left without a leader to follow, they become directionless and only able to cause harm by accident. Under a guiding force however, they carry out their commands without question.
- The Caterkillers are based on the enemy of the same name that appears in the Sonic the Hedgehog video games.