When a new pet lizard they discover grows to a gigantic size due to the effects of one of Doofenshmirtz's inventions, Phineas and Ferb try to get him back. Meanwhile, Doofenshmirtz learns a song from Jeremy so he can use it to summon an alien army with his Every-Directional-Amplifinator Gigantinator.
Phineas and Ferb hold a rodeo in the backyard with robotic bulls, Candace tries to keep focused, Dr. Doofenshmirtz competes against members of L.O.V.E.M.U.F.F.I.N. and others in an Inator Creator competition.