Phineas Flynn, Vincent Martella, and Ferb Fletcher, Thomas Brodie-Sangster, feel bored after a busy summer. To inject real adventure, the inventive duo and their friends decide to travel around the world at the speed of the Earth’s rotation, in a bold plan to craft the biggest, longest, funnest summer day of all time.
Meanwhile, Dr. Heinz Doofenshmirtz, Dan Povenmire, heads to Tokyo with Vanessa Doofenshmirtz, Olivia Olson. Vanessa starts impressed but soon becomes distraught when she discovers that her father plans to ruin the International Good Guy Convention with a giant water balloon and frame Major Monogram. She ultimately decides to leave for Paris on her own. At the same time, Perry the Platypus, Dee Bradley Baker, catches wind of Monogram’s whereabouts after Carl warns him of a suspicious note sent to the O.W.C.A. (Organization Without a Cool Acronym).
In Tokyo, the group meets Stacy Hirano, Kelly Hu, and even encounters Stacy’s cousins while scavenging vegetable oil to fuel their mission. Vanessa joins the adventure after being accidentally knocked off the Tokyo Tower by Perry’s intervention. Doofenshmirtz abandons his plan to rescue Vanessa, instead convincing Perry and Monogram to help him reach her aboard Perry’s platypus-shaped hovercar.
The traveling group, along with Vanessa, then crash-lands on the Indian portion of the Himalayas when their plane loses its wings. Phineas and friends visit Baljeet Tjinder, Maulik Pancholy, and Baljeet’s grand-uncle Sabu, Brian George, who runs a rubber band factory. Sabu sings Rubber Bands as he tours the facility, inspiring the kids with a playful idea: attach a bouncy rubber ball to the bottom of the plane to power a global hop back toward Paris and home. Their world-spanning journey is punctuated by the chorus of Bouncin’ Around The World.
In Paris, Candace Flynn, Ashley Tisdale, spots Jeremy Johnson, Mitchel Musso, among a crowd and leaves him, while Isabella Garcia-Shapiro, Alyson Stoner, grows upset because Phineas remains completely absorbed in perfecting the craft. Ferb offers Vanessa a path to repair her relationship with her father, suggesting she meet him halfway by socializing more. Doofenshmirtz, Perry, and Monogram converge to rescue Vanessa, and Doofenshmirtz feels genuine pride in his daughter’s rare act of villainy.
Back on the island, Phineas, after a desperate attempt to find a way off, sits with Isabella as the sun sinks. Inspired by her encouragement, he leans on Ferb’s giant map and turns it into a massive paper airplane. The group launches this improbable craft and rides it back toward Danville, where a road ditch stands between them and home. With one minute to spare, Buford, Bobby Gaylor, returns everyone’s bikes (though he never took Candace’s bike), and the crew vaults the ditch with a makeshift ramp, arriving home as the neighborhood recovers. The parents return, and Candace remains quietly pleased as the group belts out Summer Belongs to You. As the credits roll, Jeremy returns a bit earlier and kisses Candace, calling her his girlfriend, while Perry is last seen dating a woman at a Paris restaurant, hinting at further adventures to come.
