A second super-pupper from Krypton? Stay a while, I will be faithful... Our story starts when Krypto decides to get Superboy's attention while the Teen of Steel is, as you do, carving a giant arrow in a mountain top to help planes find Smallville's new airport. Don't worry, this will have NOTHING to do with the story, nor will his cape's apparent elasticity.
But WAIT! If this was a robot, how DID Krypto use "canine telepathy" to contact it inside the Phantom Zone? Damn you, Silver Age! You don't play fair!!!