Ferb and Phineas accidentally discover Perry's secret lair and are thrust into a spy mission of their own. Meanwhile, Candace travels on a tour bus with a girl band called "The Bettys"

Based on the fact that a platypus doesn't do very much, Phineas and Ferb create a wooden toy version of Perry to sell to a toy company. Meanwhile, the real Perry heads off to stop Doofenshmirtz from building the Great Wall of the Tri-State Area and starting up toll booths at the only exits.