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.

When Sylvester hears that a children's museum's prize exhibit is Tweety Pie, he tires to raid the museum in order to have lunch. He doesn't succeed in his mission, due to Tweety's smartness, and the children.