You all know the tale of Superman-Red and Superman-Blue... and if you don't, HERE IT IS! But did you know Krypto had to choose between two masters? How do you make that call? When he first meets the split Superman, he doesn't have to. They're together and committing their doubled abilities to Great Works, like melting polar ice caps on some planet and making the Atlanteans a homeworld.
That's one imaginary story I don't buy for a second.