When the boys build an Anti-Gravity Fun Launcher, Carl accidentally intercepts their plans and assumes they are working for Dr. Doofenshmirtz, so he is sent undercover to figure out what they are doing. Meanwhile, Doofenshmirtz intercepts the plans himself and attempts to find a use for it, and Perry tries to track down a lost goose agent.
Phineas and Ferb decide to help build floats for all the neighborhood kids in the yearly "Tri-State Area Unification Day" parade, but a family grudge leads Buford and his family to try and wreak havoc on the parade. Meanwhile, Dr. Doofenshmirtz tries to create traffic jams with a duplication device.