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.

Candace realizes that she needs to spend more time with Stacy, so she vows to spend the whole day with her only. But while visiting Jeremy and his mom, Mrs. Johnson, Dr. Doofenshmirtz's "combine-inator" zaps her and Jeremy, literally joining them at the hip. Meanwhile, Phineas and Ferb build a giant robot dog that causes a lot of mischief.

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.

It's Phineas' birthday and for the special occasion, Ferb puts together a clip show of the gang's favorite moments. Meanwhile, Agent P has to stop Dr. Doofenshmirtz from using his 'non-inator' to pre-empt his brother's biography from appearing on television.

When Candace discovers that Phineas and Ferb have invented a computer that can answer anything, she asks it how she can finally bust her brothers once and for all. Meanwhile, Dr. Doofenshmirtz loses the key to his latest invention, the "All Purpose-inator," and Agent P must find it before he does.

Candace has no choice but to go to her brothers for help after she loses her phone for the fifth time. Unbeknownst to her, the phone that they invent for her has a voice activated phone transfer app that sends her to Easter Island. Meanwhile, back at Evil Inc., Dr. Doofenshmirtz invents a "Pick 'Em Up-inator" to pick Vanessa up from class, then he finds Sarcastic Norm Head, the Norm head prototype that has an affinity for sarcasm, later Doofenshmirtz and Perry watch an exercise show.

Candace gets a bad haircut and must rely on Phineas and Ferb's hair growing machine to correct it before she attends the Endangered Animal Benefit with Jeremy and his mom. However, when Candace turns up the power, her hair grows much more than expected and she is mistaken for a rare tangerine orangutan. Meanwhile, Dr. Doofenshmirtz is developing his Very, Very 'Bad-inator.'

In ancient feudal China, Princess Isabella is part ruler and Master Perry has given up the way of the warrior. After Phineas and Ferb witness Doofus Khan capture the Princess and take her as a prisoner, they track down Master Perry and convince him to teach them his warrior ways so they can rescue Princess Isabella and save China.

When Dr. Doofenshmirtz thinks Vanessa overhears him say he would rather have a son to do his evil bidding, he feels terrible so he intends to zap her with the "Forget-about-it-Inator." Meanwhile, Norm shares his feelings of wanting to be a real boy with Dr. Doofenshmirtz and decides to play up the "son" role. Back at the Flynn-Fletcher household, Candace has Stacy hypnotize her into ignoring the need to bust her brothers so that she can spend the entire afternoon relaxing with Jeremy, but unfortunately the hypnosis trigger words end up playing right into her date with Jeremy.

After Candace injures her ankle and is told to stay in bed, she drives herself crazy trying to get her Mom's attention in order to bust her brothers. Fortunately, Phineas and Ferb provide her with a box of items to stave off her boredom. However, it ends up being more of a hindrance, until she unknowingly helps the boys warn their cosmonaut friend about a dangerous obstacle approaching them. Meanwhile, Perry interrupts Dr. Doofenshmirtz's Chicken Soup themed escapade.

Phineas and Ferb enlist the help of cyclist Greg LeMond to help Baljeet compete in a bicycle race. Meanwhile, Doofenshmirtz tries to bring the city to a standstill so he can bid on an auction unopposed.

When Ferb's cousins visit from England and challenge him to a soccer match, he and Phineas warp the walls of physics and build a high tech 3D stadium. Meanwhile, convinced that her relationship with Jeremy depends on her being more proper, Candace enlists the help of Ferb's British cousin, Eliza, to teach her the rules of etiquette. Back at Doofenshmirtz Evil Inc., Dr. Doofenshmirtz is sick in couch but forces himself to set off his \"If-A-Tree-Fell-in-the-Forest-Inator\", which causes any tree that falls to say his name.

The executive of Totally Tools oversees a contest to find the company's \"spokesanimal\", and Perry is crowned the winner. However, the victory puts Perry's secret identity in jeopardy, forcing Major Monogram to appoint Agent S as a temporary replacement, but when Dr. Doofenshmirtz sees his new nemesis is Sergei the Snail, he mistakenly underestimates his new opponent. Meanwhile, Candace has been welcomed into Mandy's "Stop the Busting" retreat, which aims to teach Candace to control the urge to bust her brothers through positive reinforcement.

Candace is bitten by a bat after watching a popular vampire movie with Stacy and worries that she is becoming a vampire. Phineas and Ferb's latest gadgets lead Candace to believe that she has indeed made the change from teenager to teen vampire. Meanwhile, Dr. Doofenshmirtz plans to change the Tri-State Area into a carbon copy of Gimmelshtump so that it will be easier to take over.

When Phineas and Ferb are inspired by an antique escape chamber that Dad acquires, they decide to build a computer-controlled tower that will trap them inside and allow them to explore the world of escapement. Meanwhile, Dr. Doofenshmirtz invents a "Rude-Inator" to ruin Roger's meeting with a visiting dignitary from England.

Phineas and Ferb create their own language, Ferb Latin, which quickly catches on. Unfortunately for Candace, she awakes from a massage puzzled to find everyone else speaking a language she doesn't understand. Meanwhile, Dr. Doofenshmirtz decides to use propaganda as his new "-inator," believing that it will work since people will believe anything they read.

The boys decide to put on a traditional family Christmas special featuring their family, friends and a few very special guests, including Grammy winning recording artist Kelly Clarkson (playing herself). The episode features three new holiday songs - Isabella's "Let it Snow", a Buford and Baljeet rendition of "Good King Wenscelas" and the whole gang singing "We Wish You a Merry Christmas".

Phineas and Ferb create their own TV shows and commercials.

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.

During medieval times, Phineas and Ferb (or, Ferb-a-lot) set off on an epic quest to find the legendary sword, Excaliferb, so they can defeat the evil sorcerer, Millifishmirtz.

After losing a gift that Jeremy made for her, Candace is determined to recreate it before Jeremy realizes it’s missing. Unfortunately, Candace can’t remember what it looks like, so she enlists Phineas and Ferb to use their mind machine to enter into her subconscious and recapture the memory. Meanwhile, Doofenshmirtz’s evil plan is to use his Underwear-Inator to take over the Tri-State Area, since everyone's greatest fear is being caught in public in their underwear.

Candace's plans to watch over Phineas and Ferb backfire when Dr. Doofenshmirtz's "Babe-inator" turns her brothers into babies. After having an epiphany, Dr. Doofenshmirtz shows up at the OWCA to give up his evil ways. Agent P has no choice but to show Dr. Doofenshmirtz the ropes of the trade, but things quickly sour between the two after Dr. Doofenshmirtz accidentally exposes the identity of a fellow animal agent.

Paul the Delivery Guy discovers his job has a higher calling to save Danville as he makes stops at Phineas and Ferb's house, Doofenshmirtz Evil, Inc., Danville City Hall and the OWCA, in a special episode seen through his eyes. The rock band, Love Händel, returns for some musical accompaniment. Meanwhile, at Doofenshmirtz Evil Inc., Perry has lost the tools in his hat.

After Mom asks the kids to keep quiet while she prepares for her online knitting test, Phineas and Ferb create ninja outfits designed to hide the wearer from anyone who is not wearing them. Meanwhile, Candace becomes increasingly frustrated after she can’t find the boys and bust them. Across town, Dr. Doofenshmirtz invents the De-Handsome-Inator.

Brigitte, Josette, and Colette, the visiting Fireside Girls from France, help Isabella capture the American Grizzly Bear, one of the world's most dangerous creatures. Buford's plan to jokingly dress up as the bear backfires when he discovers the identity of Brigitte, throwing him off his game. Back at their grandparents' cabin, Phineas and Ferb create the most amazing "run-through-the-sprinkler" experience. Meanwhile, Dr. Doofenshmirtz's loathing of pretzels drives him to create the "De-Twist-Inator" to untwist every pretzel in Danville.

Candace's plans to hang out with Jeremy are derailed after he becomes interested in playing Phineas and Ferb's newest game, jet pack volleyball. Meanwhile, when Dr. Doofenshmirtz discovers he invents "-inators" in his sleep, he decides to go back into his dreams to find out what is happening.

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.

When the boys ask Candace to decide what they should do for the day, she slyly asks them to invent a device to attract their Mom so that she can finally bust her brothers. Meanwhile, Dr. Doofenshmirtz has invented a "Baby-Cry-Inator" designed to tarnish his goodie-two-shoes brother's image with the electorate.

The guys help their dad unearth a missing piece of Danville history; Doofenshmirtz tries to make himself younger to win a children's film festival.

Candace accidentally turns into a fluid when she comes into contact with a device that turns solids into liquids. Meanwhile, Doofenshmirtz turns himself into a platypus to defeat Perry in battle.

When one of Dr. Doofenshmirtz's "-inators" zaps him and Agent P into the middle of nowhere, they must embark on a comical journey filled with twists and turns to return home.

The Flynn-Fletchers are off on an African safari, leaving Perry at home to deal with Doofenshmirtz and his most evil plot yet: to take over the O.W.C.A. But when Doofenshmirtz accidentally zaps Carl the intern with his Ultimate-Evil-Inator ray, Carl takes over the O.W.C.A. (Organization Without a Cool Acronym) and imprisons Doof and Monogram. Agent P steps in but gets zapped with Doof’s many rays and in the cliffhanger of all cliffhangers, disappears.

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.

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.

Agent P quickly figures out there is more to Norm's odd reality show that celebrates the eventful life of his creator Dr. Doofenshmirtz, which is recreated through flashbacks and special guests.