Phineas enters a thumb-wrestling competition with a local bully, while Doofenshmirtz creates a hypnotic device to control people's minds so they will sing him Happy Birthday.
Dr. Doofenshmirtz unleashes an army of helmet-controlled termites to eat all the wood in the Tri-State area, so that the population will end up buying material from his new aluminum siding business, enabling him to make a fortune. Meanwhile,as Phineas and Ferb are out pony riding at the carnival, the termites eat the fences holding the cattle, causing them to run amok all over town. As a result, they use their newfound love of a cowboy life to herd the stampeding cattle back to the carnival, while Agent P must find a way out of Dr. D's lava trap.moreless
While their mom goes shopping, Phineas and Ferb build "The Coolest Coaster Ever" as Candace tries desperately to convince her of its existence. Meanwhile, Perry battles with the evil Dr. Doofenshmirtz to stop his plan to reverse the rotation of the earth with, tin foil?!?