It's the summer solstice, so Phineas, Ferb, and their friends decide to travel around the world in one day in an effort to create the "biggest, longest, funnest summer day of all time". But not everyone believes they can actually achieve what they have set out to do, especially Buford. Candace tags along because Jeremy is on a trip to Paris, and she fears that there he may meet other girls. Also, Isabella finds her affections for Phineas sorely tested when his steadfast focus on achieving his goal puts pressure on her. Meanwhile, Dr. Doofenshmirtz takes a father trip to Tokyo, Japan with Vanessa, but sets out with Perry and Major Monogram to find her when she joins Phineas, Ferb and the others.

Phineas and Ferb's newest invention is a pair of boots that make the wearer extraordinarily fast. Candace decides to wear them so that she can be in two places at once; at Jeremy's family picnic, where she runs into Mrs. Johnson, and also at the library where she promised Mom she would read to the kids. Meanwhile, Dr. Doofenshmirtz's building is put up for sale so he tries to convince a prospective buyer, Annabelle, who turns out to be a long lost relative of the Johnson family, that it is not worth buying.

For Harbor Days Festival, Phineas and Ferb celebrate by creating a mechanical version of the historical elusive shark of Danville Harbor. Seeing what the boys are up to, Candace enlists some help to capture the mysterious shark. Meanwhile, Dr. Doofenshmirtz invents the 'Salt Water Taffy-inator' to give cavities to every kid in the Tri-State Area.

Meap's world is put in danger and the boys try to help him save the universe when they travel to Seattle. Meanwhile, Doofenshmirtz visits former nemesis Peter the Panda.

With Fall around the corner, Phineas and Ferb decide to invent "S'Fall", a colorful world full of giant leaf piles and gourds. Meanwhile, over at Evil Inc., Dr. Doofenshmirtz is mentoring Rodrigo, a budding student of evil. Unfortunately, Rodrigo truly is evil, and when he captures Dr. Doofenshmirtz and Agent P., it’s up to Major Monogram's son, Monty, to save the day.

Agent P's fate is finally revealed in the action-packed finale of the two-part television special that left Phineas, Ferb and the gang hanging...literally off an unchartered gorge and Candace frantic over a phone call with Jeremy that left their relationship status in limbo. Now, with Agent P nowhere in sight, Dr. Doofenshmirtz and Major Monogram square off against evil Carl who controls a set of familiar-looking robots to take over the OWCA, in one of the biggest battles yet.

After discovering that a strange planet is hurtling directly towards Danville, Phineas and Ferb set out to avert a disaster, while Buford looks forward to making contact with its alien race. Meanwhile, Dr. Doofenshmirtz hopes to steal the world's largest ball of twine.

Perry comes face to face with an Australian platypus hunter set on destroying him. Baljeet is having an existential emergency and finds himself incapable of making decisions.

The gang switches bodies with alien tourists for a free intergalactic vacation.

Phineas and Ferb deejay at Vanessa's Halloween party. Doofenshmirtz hunts for hidden treasure in a castle.

Doof's latest inator changes the way the Earth moves and it is up to Phineas and the gang to save summer.

In a parallel universe far, far away, Phineas and Ferb are tasked with returning the Death Star plans to the Rebel Alliance before Storm trooper Candace catches up to them. Meanwhile, complications arise when Perry is trapped in carbonite.

Doofenshmirtz's latest "inactor" turns Danville citizens into contagious zombies. Agent P. and the gang try to save the town and avoid becoming zombies themselves.

After Doofenshmirtz is defeated, a new threat in the 2nd Dimension emerges, leaving it up to Phineas, Ferb, Candace and her resistance fighters to defeat this new foe.

In this special episode, Agent P leads a rather inept team of trainees, including Dr. Doofenshmirtz, to try to stop an evil mastermind from taking over the O.W.C.A. Meanwhile, the Bug Trio continue their frivolous attempts at human communication.