Doof gathers energy from people exercising while the kids pilot a boat that surfs concrete.
Plot[]
The episode opens at Doofenshmirtz Evil Incorporated, where Doofenshmirtz's newest inator, the End-All-Be-All-inator, causes a power outage in his building. Vanessa complains that her hair dryer doesn't work, and Norm's smoothie-making is interrupted. When Doof ventures to reset the circuit, he finds a man powering a treadmill entirely by running. Inspired, he realizes he can harness human energy to power his inator.
He soon opens Doofnasium, a free fitness center where citizens' workouts secretly power his device. A tongue-in-cheek infomercial, featuring Vanessa, Norm, and a melodramatic song parodying charity ads, encourages people to join. The musical number celebrates the gym's free membership while revealing Doof's true motive: using exercise energy to take over the Tri-State Area.
Meanwhile, at the Flynn-Fletcher house, Phineas and the gang build the Asphalt Wave, a boat that can temporarily turn streets into liquid so they can "boat the boulevards." They are inspired by Candace and Jeremy's lake date—though Candace specifically told them not to follow. As the boys sail through town, Candace spots them and begins a chaotic chase with Jeremy, hoping to bust her brothers. Their pursuit becomes increasingly wild, as Candace and Jeremy's boat becomes a waterski and culminates in a call to Linda, who's distracted at Bobbi's Hair Emporium.
Back at Doofnasium, Perry infiltrates the gym and discovers the inator being powered by all the workout equipment. Doof traps Perry on a stationary bike, forcing him to pedal, but Perry's efforts overload the power grid. When Doof tries to burn off the excess energy by plugging in appliances, everything short-circuits, triggering a citywide power surge.
The surge disrupts the Asphalt Wave, sinking their craft just as Candace nearly succeeds in showing their invention to Mom. Linda's hair frizzes from the power overload, blinding her and missing the boys entirely. In the chaos, Doof's inator explodes, foiling his plan. Linda comes out of the salon to find nothing except the kids, Candace, and Jeremy on the sidewalk.
In the tag scene, the Farmer and his Wife have moved underground, and the Wife complains about lacking a boat on their subterranean lake. Just then, the Asphalt Wave crashes through the ceiling and lands perfectly in the water, to the Farmer's delight.
