Krypto was Superman's pet puppy on Krypton before being sent into space before the planet was destroyed. Upon landing on Earth he is a fully grown dog who has similar abilities to those of Superman. Krypto is adopted by 9-year-old Kevin Whitney, whose family thinks Krypto is an ordinary Labrador retriever. But the canine dons the secret identity "Superdog" when he performs heroic deeds and fights evil. Other than Kevin, the only person who knows Krypto's secret is bratty cousin Bailey, who lies so often that nobody believes his talk about the dog's powers.