In the bustling metropolis of Metropolis, Superman's loyal dog, Krypto, enjoys a special bond with his superhero owner, sharing the same superpowers and fighting crime side by side. Concerned about his master's burgeoning relationship with Lois Lane, Krypto worries he may be edged out of Superman's life. Amidst these personal doubts, a twist of fate grants powers to a ragtag group of shelter pets: a hound named Ace, who becomes super-strong; PB, a potbellied pig who can grow to immense sizes; Merton, a turtle with super-speed; and Chip, a squirrel with electric powers.

When Lex Luthor hatches a nefarious plan, Superman and the rest of the Justice League are incapacitated and snatched away. It's up to Krypto, who must wrestle with his suddenly absent powers, to lead this motley crew of inexperienced, powered-up animals. They must learn to master their new abilities, work together as a team, and overcome their own insecurities to not only rescue the captured Justice League heroes but also to thwart the villain's scheme threatening the city.