When Doofinshmirtz unleashes his army of termites to eat all the wood in the tri-state area, Phineas and Ferb use their newfounded love of a cowboy life to herd the stampeding cattle back to the carnival, but with Agent P stuck in a room filling with lava, how will he survive?

Based on the fact that a platypus doesn't do very much, Phineas and Ferb create a wooden toy version of Perry to sell to a toy company. Meanwhile, the real Perry heads off to stop Doofenshmirtz from building the Great Wall of the Tri-State Area and starting up toll booths at the only exits.

The boys and Candace hatch a plot to reunite their mom and dad's favorite band for a wedding anniversary concert.

Phineas and Ferb build super tree houses for themselves and Candace, but things get a little out of hand when a treehouse fight instigates. Meanwhile, Dr. Doofenshmirtz plans to ruin a ceremony in his brother's honor.

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.

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.

The family takes a short sail trip out to sea, but a storm causes them to wind up stranded on a remote island. To pass the time, Phineas, Ferb, and Isabella, build a set of treehouses with the most modern conveniences, to Candace's dismay, as she wants to get back home in time to attend Jeremy's party. Meanwhile, Perry the Platypus, who was left behind, must get away from the watchful eye of Baljeet and Buford, so he can go on his mission to stop Dr. Doofenshmirtz's latest plot.

When Candace finds a rabbit, she wants him as her pet, but in hindsight, he's actually a rouge agent trying to find Perry's secret lair for information. Meanwhile, Phineas and Ferb try to make x-ray glasses. And since Perry isn't around to stop his latest plot, Doofenshirtmz faces an unusual new foe.

Candace hopes to join the Fireside Girls before the Paisley Sideburn Brothers perform.

Lawrence's memory is accidentally erased by a gadget in Perry's lair before participating in a father-daughter race with Candace, so Perry operates a robot version of Lawrence to fill in for him. Meanwhile, Dr. Doofenshmirtz invents an opposite of glue named "Eulg," which breaks stuff apart rather than join it together.

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.

The boys trick out the kiddie rides at a store, Dr. Doofenshmirtz tries to burn his name into the atmosphere.

Phineas and Ferb find a chameleon in the backyard, who grows to the size of a dinosaur, thanks to Doofenshmirtz's Gigant-Inator, and takes a walk through downtown. Meanwhile, Jeremy teaches a song to Doofenshmirtz, who plans to use it to summon aliens to do his bidding.

Phineas and Ferb create a life sized maze filled with fun obstacles. Melissa, the leader of the Little Sparks, a younger branch of the Fireside Girls, is immediately captivated when she meets Candace and finds out that she was a Fireside Girl who earned 50 patches in one day. When the girls try out the maze, Candace takes charge, but things don’t go as planned. Meanwhile, Dr. Doofenshmirtz reasons that if the Leaning Tower of Pisa can generate souvenir revenue, then surely he can use his latest invention, the "Tilt-inator," to tilt buildings so he can sell souvenir replicas.

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.

The third season begins with Phineas and Ferb building a gigantic biome during a bit of bad weather to help Isabella earn a Fireside Girl patch.

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.

Mom joins Jamie Oliver as one of the judges for Danville's Meatloaf Festival Cook-off, as he stresses healthy eating and fresh ingredients. Meanwhile, Candace puts a bid on a prized souvenir resembling band members Nigel and Adrian from her favorite band, Tiny Cowboy, at the Rock and Roll Memorabilia Auction, but gets distracted when her brothers build a bounce house in their backyard. On the other side of town, Dr. Doofenshmirtz has plans to enter his family meatloaf recipe into the competition using "hate" as the special ingredient.

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.

Phineas and Ferb build a giant version of a favorite childhood game, with Danville as the central location. Meanwhile, Doofenshmirtz takes Vanessa on a camping trip.

Potato gremlins appear all over town when Phineas and Ferb clone a potato chip from Buford and it mixes with his DNA; Doofenshmirtz tries to summon the Spartan army with his historical army retrieve-inator.

Phineas and Ferb create their own TV shows and commercials.