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.

Candace finds it difficult to bust Phineas and Ferb when her brothers build nanobots that can assemble into any object they can imagine. Meanwhile, Dr. Doofenshmirtz has jury duty, so Norm takes over the day’s evil scheme -- to destroy Danville by using weapons.

A musical in which Phineas and Ferb revisit the day they built a gigantic roller coaster in their backyard. Doofenshmirtz tries to pull the East Coast to the west using tinfoil and a huge magnet.

Phineas and the gang introduce Ferb and Perry to their newest project - training domesticated squirrels to live in the wild. Meanwhile, Dr. Doofenshmirtz aims to do a better job of seeing through his evil plans now that Agent P is back.

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.

Candace ignores her brothers for a day in order to help her Mom with a bust of her own.

When Phineas and Ferb discover a commemorative coin from the 1903 Danville World’s Fair, Lawrence recounts the events of the festival to them, in which steam-driven devices were introduced and a set of kids, who were very much like them, were preparing for the highly anticipated event.

When Candace is accidentally zapped by Doofenshmirtz’s Stinkelkrampen-Inator (aka Good Luck-Inator), she realizes she has a good chance of busting Phineas and Ferb.

When Phineas and Ferb spin the house in order to paint it more quickly, Candace, inside the house, gets dizzy and collapses. She wakes up in the magical land of Odd and heads down the yellow sidewalk to Bustopolis to meet the Wizard.

Ferb and Phineas accidentally discover Perry's secret lair and are thrust into a spy mission of their own. Meanwhile, Candace travels on a tour bus with a girl band called "The Bettys"

When Baljeet saved his life, Buford vows to become his slave. Then, when Candace and Stacy accidentally send bad pictures of Candace to Jeremy's cell phone, they get a job at Mr. Slushy Dawg in order to get his phone and delete the pictures before he sees them.

The boys build a giant zoetrope that goes on an adventure of its own.

While on an archaeological dig, the boys discover a caveman who falls in love with Candace, who is dressed as a cave girl for costume party. Then, Phineas and Ferb assist Buford in locating his missing goldfish.

When Buford's goldfish goes missing, the boys help him find it out at sea. Meanwhile, Dr. Doofenshmirtz tries to destroy a tape of him 'saving' a kitten from a tree.

Phineas, Ferb, and Candace go to a Renaissance festival and Phineas and Ferb get Candace to go into a jousting tournament.

The guys decide to hold a competition between the girls to see which are better at sports. Also, the build a telescope in the backyard. Then, Jeremy's sister is tormenting Candace. Doofenshmirtz wants to be the winner of a dog show, and makes an attempt to liquefy a steak.

Phineas and Ferb create the world's largest golf course, and since Candace is sick, she asks her best friend Stacey to bust the boys for her.

The boys learn about one of Ferb's Victorian ancestors, who helped a scientist create a monster. Meanwhile, Doofenshmirtz recalls the story of his great-great-grandfather Dr. Jekyll Doofenshmirtz.

The boys create a cartoon and cast themselves as superheroes and Candace as the villain, while Perry attempts to defeat Doofenshmirtz, who has taken control of the power of dance.

The boys build a rocket ship to get a good look at a star named for them, and Candace accidentally takes a ride with them just as she is trying to find the courage to ask Jeremy to a dance, while Isabella tries her best to do the same with Phineas. Meanwhile, Perry must stop Dr. Doofenshmirtz, who, not only is conveniently in space too, but has created a massive spacestation in an attempt to get revenge on "Huge-Hands-Hans".

After taunting the boys for going to search for the "Lake Nose Monster", Candace begins freaking out on her lifeguard job, seeing the monster at every turn. Meanwhile, Dr. Doofenshmirtz tries to remove all the zinc from the lake, though even he's not sure why.

Phineas and Ferb set out to build a bigger plane than Howard Hughes' wooden Spruce Goose, so they build it out of papier-mâché, to do a similar theme to the Spruce Goose, complete with in-flight service and entertainment. Dr. Doofenshmirtz is doing his part to be green by using recycled materials to build an "Evaporator-inator" to dry up all the pools in the Tri-State area. Meanwhile, Candace and Stacy attend Jeremy's pool party only to discover an adventurous Australian girl is capturing Jeremy's attention.

When Aunt Tiana and Uncle Bob’s wedding is moved to the Flynn-Fletcher's backyard, Candace hopes that her brothers do not upstage her role as maid of honor. Meanwhile, Dr. Doofenshmirtz tries to transform food into junk food

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, Perry tries to find a lost agent, and Dr. Doofenshmirtz also acquires the blueprints to help with a parking issue on his street.

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.