Phineas and Ferb travel across the galaxy to rescue their older sister Candace, who has been abducted by aliens and taken to a utopia in a far-off planet, free of her pesky little brothers.

Phineas and Ferb get trapped in an alternate dimension where the evil Doofenshmirtz rules the tri-state area. They must find a way back home with the help of their pet platypus named Perry, who they discover is a secret agent.