To celebrate the anniversary of Perry becoming their pet, Phineas and Ferb create an enormous shuttlecock to play giant badminton. When Perry's hovercraft accidentally collides with their shuttlecock, the boys crash into Dr. Doofenshmirtz's lab and destroy his "Other-Dimension-inator", which creates portals to parallel dimensions. Intrigued, the two help Doofenshmirtz rebuild the machine. Perry arrives to stop Doofenshmirtz, but unwilling to reveal his secret identity to the boys, reverts to pet mode and is unable to stop them from helping Doofenshmirtz.