Echo Echo is a Sonorosian from the planet Sonorosia. It is a living amplifier. He can scream at ultrasonic frequencies capable of overloading machinery and stopping projectiles in mid-flight. He also has the ability to duplicate himself, not unlike Ditto, but different in that the clones aren't linked in any way, so that even if some are knocked unconscious, the rest remain active. By combining these two aspects, Ben can create the "Wall of Sound", where he and his clones can redirect projectiles back to their source by bouncing them off of strategically placed clones. He first appears in "Ben 10 Returns" when Ben fights a robotic dragon controlled by the Forever Knights.