Krypto was a white dog that was sent to Earth with Kal-El by Jor-El. When landing on Earth, Krypto has similar powers to the Man of Steel himself. A human kid named Kevin Whitney adopted him because Kal, now Clark Kent as Superman, was too busy saving the world. Krypto poses an ordinary dog near Kevin and his parents, but dubbed "Superdog" as his secret identity for his superheroic deeds, the same way Clark Kent dubbed "Superman".
Lego Batman 3
Krypto's character token can be unlocked by beating him in a race on Zamaron.