This is the list of Big Ideas in Season 3.
|"The Great Indoors"||They build a Bio Dome in which they can change the climate.||
Doofenshmirtz's Rain-inator knocks it like a golf ball.
|They get the idea from the Fireside Girls who wanted to earn certain outdoor patches.|
|"Canderemy"||They build the Robot Dog from the Title Sequence and name it Rover. They also rebuild their Molecular Separator to separate Candace from Jeremy.||
Rover: They take the wiring out, turning him off.
Molecular Separator: Rover drops and destroys it.
They have to capture Rover to retrieve the molecular separator.
The separator was from "Split Personality."
|"Run, Candace, Run"|| ||They make two pairs shoes which will allow them to run faster than a cheetah.||N/A||They take tests and conclude they can run faster than race cars and sound, but not light.|
|"Last Train to Bustville"|| ||They have a hot-air balloon race.||
Buford/Baljeet: Buford throws a model marlin out, which rebounds off a branch and bursts the balloon.
Isabella: She somehow manages to get into Phineas' balloon, leaving hers to crash.
Phineas/Ferb: They're stolen by Doofenshmirtz and the dodo attacking him.
|They finish at a train station.|
|"Phineas' Birthday Clip-O-Rama!"||Phineas follows his brother's clues for a scavenger hunt. Meanwhile, Ferb, Isabella, Buford, Baljeet and Irving host Phineas's birthday party and make a clip show.||There were many ways the disc Candace took would've been gone, in the end Candace destroys the disc herself with a wrench since she couldn't bust her brother on his birthday.||Candace prevents herself from busting Phineas, since it's his birthday. The clip show for his birthday is not mentioned after act 1.|
|"The Belly of the Beast"||They build a robotic shark.||Doofenshmirtz's Salt Water Taffy-inator breaks, sending out a string of taffy, which attaches to the shark and pulls it underwater.||They built it because they thought the other model the harbor made wasn't realistic. Candace and Stacy end up chasing it.|
|"Moon Farm"|| ||The boys decide to take some cows to the moon to see if its low gravitational pull actually does produce the best tasting ice cream ever.||A cow accidentally hits the rocket's take off button, so it goes back to the moon.||Inspired by the lost verse from the nursery rhyme, "The Cat And The Fiddle."|
|"Ask a Foolish Question"||They build a super computer to ask it what they should do for their mom.||Doofenshmirtz's Metal Unearth-Inator magnetises it and takes to his lair, then all the inventions explode.||Candace asks it how to bust Phineas and Ferb.|
|"Misperceived Monotreme"||They build a fun house inside their own house.||Doofenshmirtz's Least Likely-inator hits Candace, who clears everything up.||Candace is the one who cleans it up, after being hit with an out-of-character ray.|
|"Candace Disconnected"||Phineas and Ferb create a new super-phone for Candace after her old one breaks.||
The First Phone: A bird took the phone to its nest.
The Second Phone: N/A
Unseen structure: The museum guy takes it.
|Unbeknownst to her, the phone that they invent for her has a voice activated phone transfer app that sends her to Easter Island.|
|"Magic Carpet Ride"||Inspired by Dad's favorite childhood program, the boys decide to create a magic carpet.||A pellet from Doofenshmirtz's Stain-inator hits the rug, turning it to a different color when they land.||The magic carpet was built-in to the ground.|
|"Bad Hair Day"||They build a hair growth machine when some of Candace's hair falls out.||N/A||Candace sets the growth rate too high, which results in her being mistaken for an orangutan.|
|"Meatloaf Surprise"||The boys build a bounce house in their backyard after the one at the meatloaf festival breaks.||Buford pops it to annoy the little kids.||Buford brings it to the little kids as a gift, but then pops it.|
|"Phineas and Ferb Interrupted"||They have boring conversations all day, as they were hit by Doof's Dull-inator. They eventually build a slide to save Candace.||N/A||They also built a mini-rocket box.|
|"A Real Boy"||They built a jumping machine that launches at random moments.||It doesn't disappear, but Doofenshmirtz's Forget-about-it-inator makes Mom forget about it, and she then says "Holy Guacemole!" causing Candace to stop.||The machine does not disappear at the end of the episode.|
|"Mommy Can You Hear Me?"||They try to wish Happy Birthday to a astronaut called Sergei.||An asteroid, rerouted by Doofenshmirtz's Chicken Soup-Inator, destroys it.||An alien Ferb got to wish an old Sergei Happy Birthday.|
|"Road Trip"||When they are on a road trip, they build a "No Stop Truck Stop" restaurant on the family truck.||They drive under a bridge and the restaurant comes off.||When they drive under a bridge the restaurant gets on the bridge.|
|"Tour de Ferb"||The boys make a bicycle race track and make custom bikes to race with.||The Popup-inator blocks off Candace's evidence.||Baljeet overcomes his fear of bike racing.|
|"Skiddley Whiffers"||They make a new version of their childhood game "Skiddley Whiffers"||Candace trips on the victory bell, and the dice slips off her hands and it lands in the shoe, the cube goes haywire and makes all the games pieces advance.||Candace loves the game.|
|"My Fair Goalie"||They build a Football X-7 stadium after Ferb's English cousins challenge they challenge them to a football (soccer) match.||They give it to the Snifferton Nostrils.||Ferb disappears right before the match because he thought he was under the "Emu Curse."|
|"Bullseye!"||They build a giant game of darts across town.||Candace thinks that her mom's art project is the invention, and misses the real invention.||They keep hitting the target right about the outer ring, but Perry redirects their path and the hit the very center of a target-shaped pattern on the L.O.V.E.M.U.F.F.I.N. pageant.|
|"That's the Spirit"||They help their new friend Russell "bust" some ghosts, because he thinks his house is haunted.||N/A||The whole ghost gig ends up to be a Halloween trick.|
|"The Curse of Candace"||They build things at their friends' request. (They build a non-reflection mirror, an anti-gravity dumbbell, hidden air jets, and a plant growth lamp.)||Candace watches a scary movie, runs into their creations, and thinks she's a vampire.|
|"Escape from Phineas Tower"||They build a extremely high tower and lock themselves in so they can experience the fun of escaping.||It flies to the edge of the Milky Way galaxy and encases the whole thing.||It becomes self-aware and tries to trap them.|
|"Lotsa Latkes"||They made a machine for making potatoes using a potato chip's DNA, but instead, they make an army of mutant potatoes, since Buford's DNA was mixed in..||Doofenshmirtz's Historical Army-inator reverses and takes the machine back in time.||They built this because they have to make the potatoes because there were no potatoes in the Tri-State Area|
|"Ferb Latin"||They make up a language that everyone in Danville starts to use.||Norm adopts it. Doofenshmirtz doesn't understand him and tells him to talk normal, accidentally producing 'Talk Normal' pamphlets.||Doof pushed Norm's red button for normal talk|
|"A Phineas and Ferb Family Christmas"||They host a classic family Christmas special...in Summer||Doofenshmirtz's Transport-inator takes the set away.||The special has guest stars and some songs.|
|"Tri-Stone Area"||In 27,000 B.C., Phinabunk and Gerb (caveman versions of Phineas and Ferb) invented a wheel and they invented new car-like vehicle constructed with rock and wood.||A herd of stampeding mammoths destroy it.||At the same time, Doofengung uses his Stick-inator on one of the mammoths, though his plan backfires as the mammoths turn around and chase him. As Doofengung runs past Phinabunk and Gerb, the mammoths stampede over the vehicle, completely crushing it before "Mog" can see it.|
|"Doof Dynasty"||Phineas and Ferb find Master Perry to teach them the way of the platypus and rescue Princess Isabella.||The terracotta warrior they used to defeat Doofus Kahn eventually falls to the ground and crashes.||Takes place in ancient China.|
|"Excaliferb"||Phineas and Ferbalot go on an epic quest to find the legendary sword, Excaliferb to defeat Malifishmirtz.||N/A||Takes place during the story in a book.|
|"Phineas and Ferb and the Temple of Juatchadoon"||Ohio (Phineas) Flynn and Rhode Island (Ferb) Fletcher venture with Isabella to find her missing mother and find the lost Temple of Juatchadoon.||Candace takes pictures of the whole quest, but her camera is all washed up (literally).||This episode takes place during the summer of 1914.|
|"Monster from the Id"||They build a Mind machine to go deep into Candace's subconscious to retrieve how Jeremy's gift looked like.||Baljeet takes off the cables of the machine.||Originally it was going to be used for Baljeet.|
|"Gi-Ants"||Build the Antius Maximus, to wonder how it would be like living as ants.||Doofenshmirtz's Turkey-inator hits the Antius Maximus and the now enlightened ants bring it with them to outer space.||Candace was made the ant queen due to excessive ant pheromones.|
|"The Remains of the Platypus"||Phineas and Ferb build Cheesetopia and a Celebration seeking rocket||
Celebration seeking rocket: Launches and travels to Doofenshmirtz's party.
Cheesetopia: Doofenshmirtz's Vaporizor-Inator hits Cheesetopia.
This episode starts from the end and works its way back to the beginning.
|"Mom's in the House"||Phineas and Ferb build the Perrytronic-3000||Doofenshmirtz Duplicate-Inator 2 hits the Perrytronic-3000 resulting in two Perrytronic-3000's, one hits the tail of the other and they somersault out of the backyard.||Candace did a "B.B. Busting" technique where she tried to stop the kids from finishing the invention so it doesn't disappear, yet that fails.|
|"Perry The Actorpus"||Phineas and Ferb enter Perry into a company contest and Perry is crowned winner.
Positive Reinforcement Machine that Mandy uses.
|Totally Tools Sponsor: Perry uses Doofenshmirtz Mustache-Inator and hits every advertisement with it, causing them to be replaced with Sergei the Snail.
Positive Reinforcement Machine: Candace angrly destroys it after learning Phineas and Ferb made it.
|Perry's picture on the billboard made him too recognizable to be a secret agent.|
|"Let's Bounce"||Anti-Gravity Maximus and Trampolines||Doofenshmirtz Tell-the-truth-Inator flies around aimlessly and catches all the trampolines and the Anti-Gravity Maximus.||Doof also makes an Abe Lincoln robot to match the theme of his scheme.|
|"Bully Bromance Breakup"||Phineas and Ferb assist Baljeet in climbing the Danville Mountain.
Phineas and Ferb build an ice chalet
|Phineas's ice chalet is destroyed when the mountain, sculpted into Doofenshmirtz face, crumbles.||Phineas and Ferb almost go insane because Baljeet didn't let them build.|
|"Quietest Day Ever"||Phineas and Ferb create ninja suits that hide the wearer from anyone not wearing a suit.||Remove their ninja suits, then turns it on, making their suits put themselves away.||They also make one for Candace.|
|"The Doonkelberry Imperative"||Phineas, Ferb and Isabella go to Drusselstein and find some Doonkelberries for Doonkelberry pie and help fix Drusselstein's major powershaft. They also build a catapult and a warp generator to bends the fabric of space-time and makes areas of the world closer together.||Candace leans on a button of an inator at Doofenshmirtz Evil Inc. while looking for a book, making the catapult dissapear.||Baljeet turns off the warp generator while Dr. Doofenshmirtz is slingshoting himself, so he falls in the ocean.|
|"Meapless in Seattle"||The boys' "Cute-tracker" lead the gang to Seattle and an adventure to save the universe. They also build giant pillows for giant pillow fight.||Giant pillows were pulled up by Mitch's machine.||Originally a fake Big Idea, but was later made into a real one.|
|"Delivery of Destiny"||Phineas and Ferb builds city-wide amusement park on a single track||Doofenshmirtz's Juice-inator hits their one track amusement park, turning it into juice.||N/A|
|"Buford Confidential"||Phineas and Ferb build an underwater water slide||None, but Doofenshmirtz's De-twist-Inator straightens it out.|
|"The Mom Attractor"||Phineas and Ferb build a Mom Attractor||Doofenshmirtz's Baby-Cry-Inator makes the Mom Attractor run to the giant crying baby.||Candace asked Phineas and Ferb to make the invention.|
|"Cranius Maximus"||Phineas and Ferb invent a cerebral stimulatory hat, or "Brain booster" to help Baljeet.||Buford's wedgie machine pulls Baljeet's machine and the Brain Booster into space.||Phineas and Ferb don't construct the invention in this episode, but Baljeet does.|
|"Agent Doof"||As babies, Phineas and Ferb upgrade their stroller with a motorbike.||N/A||Phineas and Ferb were turned into babies thanks to Doofenshmirtz's Babe-inator.|
|"Minor Monogram"||S'Fall (Combination of Fall and Summer)||One of Doofenshmirtz's propellers blows all of the leaves away.||Second time Phineas and Ferb combines two seasons|
|"What A Croc!"||Phineas and Ferb attempt to find Crikey the crocodile||Crikey eats Irving's UPAFDS, causing Candace to lose the evidence.|
|"Sci-Fi Pie Fly"||Phineas and Ferb build a spacecraft to investigate crop circles||N/A||Candace took a "Me Day" and did not bother to bust them.|
|"Sleepwalk Surprise"||They play volley ball with jetpacks.||Doofenshmirtz's Cupcake-inator turns the ball into a cake, then the Hug-inator makes the net hug the jetpacks, then the Confetti-inator turns the net and jetpacks into confetti.||Candace tried to prevent Linda from seeing them due to Jeremy joining them.|
|"Sipping with the Enemy"||Phineas and Ferb put on an enormous backyard magic show.||Phineas makes the whole stage disappear as the final act, and the parents are turned hip by the Cool-inator, making them ignore Candace.||N/A|
|"Tri-State Treasure: Boot of Secrets"||Phineas and Ferb help their father unearth a missing piece of Danville history when they run into his lifelong nemesis Worthington at a flea market.||Doesn't disappear, but Phineas and Ferb made a short movie of their adventure.|
|"Doofapus"||Phineas and Ferb create The State-of-the-Matter Transfer Device to turn anything into liquid so they can have instant smoothies.||The Double-Inator hits their device, doubling it, and they hit each other, turning both into liquid piles.||The State-of-the-Matter Transfer hit Candace, making her liquid.|
|"Norm Unleashed"||Phineas and Ferb build nanobots that they can assemble into any object they imagine.||Doesn't disappear, but a squirrel hits the remote, dissassembling the nanobots before Linda sees it.||Corresponds with the theme song.|
|"Where's Perry?"||Phineas and Ferb build a highly unconventional vehicle to explore an unchartered gorge.||As it fell, it crashed. Then Doofenshmirtz, Major Monogram and Carl pick it up cleaning the robotic parts with the Magnet-inator, as seen in the second part.||Buford breaks the machine, making the boys to fall to the gorge.|
|"Ferb TV"||Phineas and Ferb shows Candace what they come up with for television shows.||Unnamed inator disappearance receiver to Ferb TV.||N/A|
|"When Worlds Collide"||Phineas and Ferb observe an incoming planet and use a spring to push the planet into space.||The spring gets attached to the planet and is pulled along with it.||Candace couldn't try to bust them until mindnight because she already failed alltogether once today. This took place immediately after "Gi-Ants".|
|"What'd I Miss?"||Phineas and Ferb teach domesticated squirrels how to be wild again.||A water droplet hits the backyard, and using the little surfboards, the squirrels surf out of the backyard. Candace successfully tells the story, but the activity is not considered bad.||The Big Idea took place the day before the episode. Ferb didn't know about this because he was at Debate Camp.|
|"Road to Danville"||Phineas and Ferb with the rest of the crew decide to create a quilt.||
|Candace most likely did not bust her brothers due to their activity being, as Candace would dub it, 'Non bustable'.|
|"This Is Your Backstory"||Phineas and Ferb play ping pong to store enough kinetic energy to create a quantom vortex.||Sucks in itself||N/a|
|"Blackout!"||They build a unknown device to have the best blackout ever.||A Jetpack Squad takes it to give it to Doofenshmirtz.||Exactly what they built is unknown. However, Candace accidentally rode it.|