Slash asked them if he could do a song for the movie. That's right. THE Slash.
Candace's determination to bust her brother's can lead to one of those. Great examples are in "Bubble Boys" and "The Belly of the Beast"
Anything Perry does when in agent mode, really.
Lawn Gnome Beach Party of Terror
Phineas tricking Buford using a holographic projection of himself.
"FOLLOW UP SINGLE?! Who do you think we are?! Some two-bit hacks who keep writing songs just because you pay us OBSCENE AMOUNTS OF CASH!? Phineas and the Ferb-Tones are strictly a one-hit wonder! GOOD DAY TO YOU, SIR!"
Ferb oneshotting Buford by pinching his neck.
"Well, he was getting all up in my face."
Doofenshmirtz actually managing to re-trap Perry after Perry had escaped from his first trap!
Ready for the Bettys
Candace finally calling out the Bettys for taking advantage of her and Stacy.
Phineas, Ferb, and Agent P saving the Bettys and their bus.
Get That Bigfoot Outa My Face!
Phineas and Ferb's trick at the campfire. Immediately topped by the one played by Candace and their grandparents.
Journey to the Center of Candace
Perry taking down Doofenshmirtz within ten seconds when he indirectly threatens the boys' lives.
It's About Time!
The Fireside Girls building a time machine to rescue Phineas, Ferb, and Candace with nothing to go on except for a (flawed!) blueprint. And they do it from scratch. Even Phineas and Ferb had had a semi-complete (if non-functioning) model to work with. Is it any wonder that they're the ones who help out with the boys' projects all the time?
Dude, We're Getting the Band Back Together
Phineas: Can we help?
Lawrence: Well, I'm afraid not, unless you can perform miracles.
Phineas: ...what's your budget?
And of course, he was right.
The Concert Kiss scene: "Well don't just stand there, KISS HER!"
Just as it looks like Love Händel will break up again, Ferb opens the garage door and reveals the huge crowd of fans standing outside.
Buford using Baljeet as an axe. Even better, Baljeet looked pretty fired up about it as well. (In fact, he suggested it in the first place. Sort of.)
Isabella turning Buford's "no-rules" attitude around on him, chaining his chariot to the side of the road.
Leave the Busting to Us!
Perry seeing through Doofenshmirtz's "fake window" trick and faking him out.
Crack That Whip
Admittedly much less spectacular than some of these, but the way Ferb dodges Suzy's attack is oddly awesome. It's actually aided by his completely blank expression, which basically sends the message "I could do this in my sleep if I wanted to, kid." He wasn't even LOOKING when dodged!
Voyage to the Bottom of Buford
Buford getting over a fear of giant squids and then defeating one in just one hit.
Also his flashback showing him beating up the much bigger previous local bully even before he became a bully himself. Notably, in both cases he was protecting his goldfish.
Traffic Cam Caper
Perry's inexplicably convincing Ferb disguise.
The entire bowling ball/pinball game, including Perry making use of it to defeat Doofenshmirtz at the end. Some highlights include:
Isabella when keeping the ball in play. She goes up to a man at the carnival and pays to play his rigged game of hitting the bottles. She pays, takes the ball, winds up...and then calmly waits for the giant bowling ball to crash into the stand. Maybe you have to see Isabella's smug expression to get the full effect, but it was great.
Man: ...Take your pick. Anything from the top.
Ferb comes to a stop beside a fruit stand as the ball is falling from the air. After a moment of consideration, he moves the stand keeper a bit to the side. Moments later, the ball lands on the fruit stand, splattering pulp and juice all over everything and everyone present— except for Ferb, who has positioned the stand keeper in just the right place to shield him from the mess.
Phineas and Ferb break three world records at once. Presumably they do so on a regular basis, but this is one of the few times they get recognition for it (albeit as part of the "World's Most Pointless Records").
Even better, he pulls them completely out of nowhere (which Doof lampshades).
The Flying Fishmonger
The final successful jump across the gorge.
One Good Scare Ought to Do It!
Isabella and her Fireside Girls forming a trampoline instantaneously using their sashes in order to save Phineas's life.
Phineas and Ferb Get Busted!
Candace becoming an emotional wreck to save her brothers, followed by perhaps the most empowering usage of Phineas's "I know what we're gonna do today" line on the show.
Which is then followed by Perry unhesitatingly showing up in one of Dr. Doof's -inators and using it to get rid of the Sergeant, then departing with a completely Badass tip of his hat and an "I've got this covered" expression. (Oh, and he was simultaneously fighting Doofenshmirtz the entire time.)
"I'm going to bust my brothers... out!"
Perry escaping from his trap by replacing himself with a dummy offscreen... somehow...
Perry Lays an Egg
"How does it feel to have your platyposterior handed to you on a plate, son?"
Gaming the System
Candace fighting and defeating Giant Buford. While wearing nothing but a towel and hair curlers, no less.
The defeat, of course, consisting of beating the crap out of him with her own health bar.
Followed by Isabella defeating the next Giant Buford boss using a camera.
The Chronicles of Meap
After souping up the alien ship that crashed into the yard, Ferb goes for a joyride and happens to drive past his crush, Vanessa Doofenshmirtz. He stops, drives back to her, rolls down his window and flirts with her. He then flies off amazingly fast. Even though she is sixteen and he is "less than 15", she looks genuinely impressed!
Candace's Big Damn Heroes moment, using Phineas and Ferb's baseball shooter to effortlessly wipe out a group of robots.
It was foreshadowed from the start, but Meap turning out to be a PintsizedBadass Adorable with a rainbow death ray and swiftly dispatching Mitch was still awesome.
Even more impressive considering that "Meapless in Seattle" revealed that Mitch is really a Meapian inside a mechanical suit, and that not even Meap was aware of this. Meap took down a mechanical suit with physical blows alone, without even knowing that he was fighting a mechanical suit, and probably does so with some regularity.
Thaddeus and Thor
Phineas and Ferb revealing the rest of their (previously seemingly plain) fort.
Dr. Doofenshmirtz finally making a successful (and extremely epic) kick in kickball (even though he still gets tagged out because he was too busy bragging about it).
Though more mundane, there's Doofenshmirtz's cup-stacking skills and the fact that Candace later breaks his record.
Oh, There You Are, Perry
Doofenshmirtz's defeat of the Regurgitator.
Hide and Seek
Phineas, Ferb, and their friends (and Irving)note except for Baljeet, who spent half the episode inside adead fly, which on some level arguably constitutes as a moment of awesome in itself defeating a robot using needles and thread. Also Ferb rewiring it in less than a second to become a flying machine afterward.
Isabella being the one to knock it out by pulling its leg out from under it.
Baljeet finally snaps when he's told that he won't be graded for summer camp (which he had thought was a geology camp when it was really a rock music camp). So he storms onstage and demonstrates his hidden Power of Rock, and it is awesome.
It's the best the first time you see it. The entire episode is funny, but the whole time you just get the feeling that Baljeet will HAVE to do a song. You're terrified for Baljeet and your eardrums for the entire episode, until Baljeet storms up on stage and sings the first line. And then your head explodes, because it just gets better and better.
When Doofenshmirtz - without blinking an eye - uses his helmet-mounted 'Away-inator' to zap the biker who makes a pass at Vanessa.
Dr. Doofensmirtz: "She's sixteen!" ZAP!
Ferb's rescue of Vanessa at the end of the episode qualifies. Rescue Romance, anyone?
Vanessa showing her mad skills in the "I'm Me" song. Just about everything Ferb does in that sequence too.
Phineas and Ferb's Quantum Boogaloo
Basically the entire episode - it really had an outstanding story to it. While the boys getting busted was rather heartbreaking to watch, and the part with Doofenshmirtz becoming ruler was scary, once bad future Candace returns to the good future is when it really kicks into high gear.
Phineas and Ferb Musical Cliptastic Countdown
Major Monogram: Okay, that doesn't even make sense.
Dr. Doofenshmirtz: It doesn't have to, I've got a monster truck!
He then makes a spectacular exit on said truck. Monogram is stunned for a moment, then he tries to finish what he was saying... only for Doofenshmirtz to drive back and run over his feet!
Doofenshmirtz is predictably trapped in a cage at the end, and Monogram smugly asks him to say goodnight to the audience. The audience is expecting him to say something like "Goodnight to the audience", but what does he say instead?
Dr. Doofenshmirtz: You know, one day, I'll get out of this cage. But your name will still be Francis.
Perry defeating the hypnotized audience by revealing the #1 song on the countdown.
Isabella and the Temple of Sap
The entire sequence where Isabella and the Fireside Girls retrieve the maracanut tree from the abandoned amusement park and obtain the sap Phineas and Ferb needed for their project.
Cheer Up Candace
Perry is framed by Dr. Doof and is about to be arrested by the other agents, but he easily escapes and they end up handcuffing each other. Later in the episode, he has to fight almost all of his doppelgangers that Doof had created (and used to frame him in the first place) and handily defeats them.
Fireside Girl Jamboree
Though it turns out to be unnecessary and she had help from Phineas, Ferb, and Isabella, it's still impressive that Candace succeeds in earning 50 Fireside Girl patches in one day, accomplishing feats like wrestling an alligator and running all the way up to the top floor of Doofenshmirtz's building in order to do so.
Doofenshmirtz intercepting Perry's helicopter with a giant robotic arm before his jingle ends.
How Perry disposes of the L.O.V.E.M.U.F.F.I.N. members, even by Agent P standards. He pulls out two huge knives and cuts various heavy objects from the ceiling to drop onto the evildoers below. This is one of the few times Doofenshmirtz is seen hospitalized in the aftermath of his defeat.
Perry coming back to save Doofenshmirtz from his mutated plants. Using a chainsaw.
Ferb tossing a paper-maché boulder straight to the top of the replica Niagara Falls.
Phineas: You know, even though I know that's paper-maché, that's still an impressive throw.
After Doofenshmirtz tricks him into falling out of a blimp, Perry proceeds to pursue and foil Doofenshmirtz using a banana truck, all with a platypus-themed truck-driving song playing on his CD player.
The first time we see Major Monogram goes into the field himself, he goes with a small army.
To elaborate, Candace is falling down a canyon on a rocket powered by quarters, but she doesn't have any quarters left. Ferb casually parks his rocket on a side of the canyon, catches the attention of a couple of tourists, does a robot routine to earn a quarter, then slingshots said quarter directly into the quarter slot moments before the rocket hits the ground.
Phineas and Ferb-Busters!
Doofenshmirtz gets a more advanced robot to replace Norm, and a lot of time is spent hyping up how much better it is. However, when hit with a wave of energy, the robot transforms into a Humongous Mecha and decides that it needs to destroy Doofenshmirtz. After it easily flicks Agent P out of the building, it's up to the unaffected Norm to protect Doofenshmirtz. He promptly takes the much larger and more advanced machine down. With a cup of coffee.
Doofenshmirtz handily winning the inator competition, uncharacteristically putting his Genre Savviness to good use.
"Let go of the balloon!"
Phineas and Ferb's solution to having to both rescue Isabella (who is dangling from a building) and prevent a billboard from falling on the crowd below while in their superhero suit. Phineas gets out of the suit to save Isabella as Ferb (who only has control of the suit's lower body) shatters the billboard to little bits by spinning through it using the suit, all the while not breaking their cover to Isabella.
Phineas and Ferb Hawaiian Vacation
Doofenshmirtz steals Perry's boat and flees the island... only for Major Monogram to pop out of the sand and reveal to the audience that Doofenshmirtz had been set up all along. During the credits, Doofenshmirtz's escape is put to an end when he is eaten by Agent W (a whale).
Nerds of a Feather
As leaders of two separate fandom groups, Baljeet and Buford spend most of the episode engaging in a rather unhealthy rivalry over whose franchise is the best, until their fighting is interrupted by the sudden appearance of a giant monster (actually an animatronic effect). When Buford tries to run away, a strict Baljeet stops him and asks him if Odar Underhump (the character Buford is cosplaying as) would've run away from danger. Buford gets his point, and the two decide to unite their fandom groups to fight against a common enemy - Which is exactly what Phineas was hoping they would do.
We Call it Maze
The project of the day is essentially a live-action Professor Layton game. Probably unintentional, but still extremely cool.
Near the end, Doof ends up in a junkyard where Vanessa and her friends are partying (don't ask) and a mishap causes his hands to be glued to the turntables. This stops the music, which pisses off the teens. But then, rather than leave his archnemesis to be humiliated in front of his daughter, Perry slaps the mind control helmet from earlier in the episode on Doofenshmirtz and starts making him... bust out some awesome beats. Hell ya.
Made even better by the fact that Perry left the controls behind about halfway through the song, so Doof was doing it all on his own from there on.
Phineas, Ferb, and their friends helping Perry defeat Doofenshmirtz by controlling Perry in perfect sync with one another. (They thought they were playing a video game. It's a long story.)
Rollercoaster: The Musical!
The entire episode. Why? Well, for one, it is the SECOND time they go back to the pilot, cross-reference it and play around with it to hell and back. Second, it consists almost entirely of songs, whereas the original contained none, as if the directors figured "Fuck it, let's fix that." And just to go completely nuts, not only does it at seemingly random either expand or mix up the jokes they repeat from the pilot, but the whole thing ends with a big dance number featuring practically every single character that has ever appeared in the series so far. Had this been the end of the series, it would have possibly been the biggest, most spectacular Disney animated series finale ever, only rivaled by "Summer Belongs To You". And when you think about it, the fact that they can make a special and a regular episode that both feel like perfect ends to the series so soon after another is a Crowning Moment of Awesome for the entire creative team.
At the start of "Carpe Diem", Phineas hopes the musical wasn't anticlimactic. If anyone thought so at the start of the song, they probably sure didn't by the end of it.
The sheer Continuity Porn in "Carpe Diem" makes it one (among many) of those Phineas and Ferb segments you just have to watch over and over again in order to catch all the little details (and for the song as well, of course).
Candace gets a minor one:
Princess Baldegunde: Candace, I need to ask you question, how is pronounced the name of cute blonde boy with guitar?
Candace: What cute blonde boy?
Princess Baldegunde: The one with band! Is it Jerr-emy or Jer-mee?
Candace dismantling almost the entire train to provide enough fuel for it to keep going up the mountain.
Phineas' Birthday Clip-O-Rama!
Candace decides to for once really fight against her Cosmic Play Thing fate and performs quite the impressive stunts to preserve the DVD that contains all the proof she will ever need for all of P&F's projects. I mean, we even have a kid asking her for an autograph after all of that. Bonus points because of what happened next, but you should read the heartwarming entry to learn about that.
The epic Bait and Switch in the way Doofenshmirtz's machine comes into play with the A plot.
Phineas and Ferb Interrupted
The boys get hit with a "dull-and-boring-inator" and become just that, and it's actually sort of depressing to watch (all Phineas wants to talk about is grass growing, the weather, and plain oatmeal...) Meanwhile, Perry the Platypus attempts to rewire the -inator to make it work in reverse. Then he starts shooting it off, and of course a casual viewer would expect it to eventually hit Phineas and Ferb and bring them back to normal. But Phineas and Ferb are far above a simple fix like that, and when Candace is in trouble, they snap out of it all by themselves and instantly create something to rescue her.
Buford: I still think we should get a ladder.
Phineas:(blank stare) No... that would be... boring. Wait a minute... I know what we should have done today!
Mommy Can You Hear Me?
The epic piece of utter Mind Screw at the end. You might have to play it back. Several times.
Doofenshmirtz dousing himself in honey to draw a swarm of angry bees away from Vanessa and her friends, all of whom were allergic to bees. And this after it had been established that a bee sting (followed by a string of other hilarious traumas) was the worst memory he had of camping
Jeremy finally catching on and messing with Candace's head. He gets some grade-A snarking in before she decides 'To heck with it' and abandons her latest ploy to impress him. Yes, Jeremy just got one of these.
Even if it missed, there's Ferb's impressive kick to his cousin's goal post. Also, even with his "curse" and all, he was still directly responsible for all but one of the other goals his team scored. The one exception was awesome as well, we have Ferb busting out some insane moves before passing the ball to Phineas, who uses the shape of his head to make the goal.
Lawrence, of all people, revealing that all this time he had been letting Adrian win their various competitions on purpose to make him happy. And just as it looks as though he's actually about to lose their game of "Keepy-Uppy" legitimately when he slips and sends the ball flying straight up in the air, he just gets up, gives a short and extremely calm speech about how one shouldn't jump to conclusions so quickly, then intercepts the ball before it hits the ground and really gets into the game (which he quickly turns into his victory dance). At least we know where Ferb gets his modesty and Minor In Asskicking now.
Doof shows a ton of Genre Savvyness by winning the Mechanical Mom competition in one shot. Specially because Rodney earlier helped establish that it was very easy to fail that competition.
At the episode's climax, a pumpkin-headed ghost is stalking toward the kids and everybody - Phineas and Ferb included - are clearly terrified of it. They go on to realize that 'hey, something doesn't match up here' and go from scared to determined (or possibly curious) within seconds of this realization. Just to drive the point home, Ferb picks up a nearby 'skull' and pitches it at the ghost, breaking it and revealing it to be a robot in one hit.
Phineas: Wait a minute, if you're a ghost and you have a pumpkin on your head, what does that make you when you were alive?
Ferb: The probability of a human-vegetable hybrid is exceedingly remote.
Escape from Phineas Tower
Phineas and Ferb have a lot of these after the computer goes nuts courtesy of Doof's invention of the week, specially at the end, when they finally defeat it with a logic bomb of sorts.
In three seasons, they've attained such a high level of awesome that they now have to build an AI more intelligent than them to trap them repeatedly and possibly kill them in order to alleviate their boredom. That is awesome.
A Phineas and Ferb Family Christmas
Perry makes putting up Christmas decorations look badass.
One for the creators - even with every character speaking caveman gibberish, the Once an Episode moments and series in-jokes come through loud and clear. (It helped that pretty much everything was lampshaded to heck and back, often by the creators themselves.)
Apply some Fridge Brilliance: if stone-age Phinabunk and Gerb were able to invent the wheel, doesn't that imply that someday, Phineas and Ferb are going to invent something that'll change the world just as much? These two boys are a walking technological singularity.
Alternate Buford and Baljeet defeat dozens of castle guards in combat. Worthy of note is that Baljeet was fighting without a weapon.
Alternate Phineas and Ferb dodging Doofus's booby traps. Unfortunately, both this and Buford and Baljeet's moment happened largely offscreen.
During the training montage, Baljeet karate chops a wooden plank... and completely fails to damage it. However, he does succeed in completely disintegrating the cinder blocks supporting the plank.
It's VERY subtle, but Candace follows the technology-using Phineas and Ferb up the Unclimbable Mountain of Unclimbable-ness completely unassisted. Twice, actually.
The gang beating up Doofenshmirtz's dragon with a giant terracotta warrior and Perry coming out of his retirement for a Big Damn Heroes moment afterward.
The "Epic Monster Battle". The most METAL thing you will ever see on a Disney show aimed at kids.
Phineas and Ferb and the Temple of Juatchadoon
Perry's Big Entrance. Not to mention foiling Doofenshmirtz with his fez.
Doofenshmirtz: Perry the Platypus, you totally one-upped my entrance!
Candace's demands accelerate the development of the ant society so quickly that they soon become fully sapient spacefarers.
The Remains of the Platypus
How Perry snaps out of being turned into Doof's servant. He wrote a reminder to himself on his chest right before he was brainwashed that he would see when he looked in a mirror. It works.
Carl also deserves credit there for spilling juice on Perry's suit, causing him to go change and look in the mirror. It was unintentional, but Carl of all people got Perry out of that mess.
Perry The Actorpus
Sergei the Snail. To elaborate, Sergei is so small that Doofenshmirtz needs a magnifying glass at first to see him properly, and needless to say moves along at a snail's pace, but on his entrance he breaks down the door and due to Doofenshmirtz's usual traps not fazing him in the slightest, he just keeps coming until Doof finally figures out his Weaksauce Weakness (salt). Then once he's freed, he shakes Doofenshmirtz around and flings him clear across the room like it's nothing.
In a meta sense, it can be quite satisfying to see Suzy finally get caught for her misdeeds.
Bully Bromance Breakup
Baljeet does a number of outlandish and awesome stunts and bad-ass things when the gang is climbing up the mountain, including running across a rope bridge and using it as a way to swing across the river when it breaks beneath him.
What makes it even more awesome is that Baljeet was doing it without using one of Phineas and Ferb's inventions.
Another awesome Baljeet moment is him giving Buford a wedgie. Yeah, you read that right.
And using Buford's extended underwear to form a parachute, allowing everyone to safely glide down the crumbling mountaintop.
Quietest Day Ever
Perry's elaborate system of mirrors that he uses (twice!) to foil Doofenshmirtz.
Meapless in Seattle
Perry and Peter working together to save Doofenshmirtz from Mitch.
And the combination of acrobatics with fighting evil has got to be a nod to Nightwing of DC.
Vanessa tearing apart the metal trap holding Perry with her bare hands.
When Ferb is questioned on where he learned his volleyball serving skills:
Ferb: At the Yorkshire Athletic School for In Your Face.
Sci-Fi Pie Fly
It's pretty impressive that Candace not only takes a day off from busting Phineas and Ferb, she successfully resists her normally-irresistible urge to bust her brothers. Several times. Even when the flying saucer they built is still there at night, she does nothing about it and just goes back to bed. It's especially impressive considering all the episodes in the past where she's tried-and failed-to quit busting her brothers (like "Last Train to Bustville", "Hip Hip Parade", and "Perry the Actorpus").
Tri-State Treasure: Boot of Secrets
Though it's actually part of a movie Phineas and Ferb made, there's the alien army, complete with cameos of several previously-appearing characters.
Platypus!Doof and Perry battle each other. They are continuously even matched, making it quite nail biting.
Also surprising, as one might not expect Doof turning himself into a platypus alone to help much considering his opponent is not only a platypus but also a well-trained secret agent, and yet it does somehow make him more proficient in battle.
Norm gets a big one when he has to take over for Doofenshmirtz and nearly beats Perry in the process, not to mention almost succeeding in conquering the Tri-State Area. Behold. There's also the fact that it's implied Norm is the one who retrofits himself with all that new weaponry.
The rematch where Perry returns the favor by using Phineas and Ferb's nanobots (which can transform into anything the user desires) deserves mention as well.
Doofenshmirtz's ploy at the beginning of the episode (tricking Perry into thinking he had blundered and destroyed his own inator of the day) is actually surprisingly effective, and may well have succeeded if not for his own really bad luck.
Carl gets a song for the first time, and not only is it awesome, it's a Villain Song to boot.
Where's Perry? (Part Two)
Carl is shown to be the most scarily competent villain in the series.
The entire fight between Perry, the agents, Candace, and Monogram and the robots.
Major Monogram showing he's more than just the head of OWCA: by punching/kicking/ripping apart evil robots by himself and tossing parts of them to Doofenshmirtz for use in construction.
Robot Candace Taking the Bullet when a robot Phineas is about to blast the real Candace, and destroying the robot Phineas moments afterward.
Robot Candace: You're busted.
Phineas rescuing the others while dangling from a ledge, followed by Baljeet rescuing Buford with a nice Awesomeness by Analysis moment.
Monogram revealing his private jet.
Doofensmirtz really shows his stuff with the "Turn Good"-inator, making this one out of parts pulled from said jet in flight and finishing by the time they reach Africa.
Buford pulling up the rest of a gang onto a ledge all by himself.
When Worlds Collide
Upon realizing that Earth is in immediate danger of colliding with another planet, Phineas and Ferb casually construct a giant spring to deflect the incoming planet, saving both worlds.
This Is Your Backstory
Phineas and Ferb's table tennis match. And it's not just an Overly-Long Gag, they were actually building up enough energy in the ping-pong ball to create a quantum vortex.
Near the end of the episode, Doofenshmirtz reveals to Perry that the reason the scheme of the day was a game show involving his emotionally-scarring backstories is that he's been collecting the memories of his over the course of the episode because, since great evil is dependent on such backstories, he's been storing the memories in a huge vat and will put them back in his head all at once to increase his evilness. Right as he's about to store the backstory that will fill the vat, Perry knocks the memory extraction helmet off of Doof's head - thus giving him a humiliating memory that will fill the vat. Doof, of course, acts upon this.
Doofenshmirtz: (paraphrased) Remember two seconds ago when you knocked the memory extraction helmet off my head? No? Well, I sure do!
For Your Ice Only
Hockey Z-9. That is all.
Happy New Year!
Perry being Genre Savvy by letting Doofenshmirtz make everyones' New Years resolution to make him their leader, only for Doof to realise that nobody ever fulfills their resolution, thus leaving him defeated.
My Sweet Ride
The song "My Sweet Ride" is an absolute Crowning Music of Awesome, but Ferb's finger-pointing on the line "Boom ba-ba-boom ba-bang-ba-bang-bang" is absolutely Monty Oum-like.
The entire opening scene in Seattle is one. Specifically, Perry on a high-tech platy-cycle.
Agent Lyla's reveal that she messed up Perry's chase scene on purpose, knowing that the criminals would lead her to Banister.
Doof got a subtle one in the fact that he kidnapped a train and managed to tie up the conductor without anyone even noticing.
Peter the Panda coming in out of nowhere to capture Bannister, and Perry's reveal that he texted Monogram for backup.
Doofenshmirtz managing to climb up to Bannister's helicopter mere moments after Perry and Lyla, despite not having a grappling hook.
Liam's platypus hunt, with Perry - sorry, Steven and Doofenshmirtz successfully avoiding him and eventually being able to defeat him.
Perry's complete mastery of Boomerangs. Makes you wonder why he doesn't have one with him all the time.
Right before he shows his stuff, Liam tells him to put the boomerang down, claiming that platypuses can't throw boomerangs. Perry just gives an absolutely smug look that leaves one without the slightest doubt that Liam is about to get his ass whooped.
Liam's impressive arsenal of boomerangs, including a giant one that slices off the top of a hill and ends up being a literal Chekhov's Boomerang.
Perry uses his venom spurs for the first time ever on the show.
Candace using the power of square dance calling in order to get the aliens back on the mind share platform before it self-destructs.
A subtle one: According to Red's narration, the kids had to tunnel through the prison wall, crawl 500 yards through gunge, find the needed parts, and crawl back through the gunge in order to rebuild the alien communication device. According to the self-destruct timer on the mind share platform, they did this in just over 10 minutes. That's a CMOA for Phineas and his friends, and a sign that the galactic prison really needs a security upgrade.
Backyard Hodge Podge
The invention in this episode was purely made out of spare parts from previous inventions, yet the final result was still quite impressive.
Isabella giving Bluto's speech from Animal House, complete with "Forget it, she's rolling."
Ginger gets to lead a song for the first time in the series.
Great Balls of Water
Phineas and Ferb create a giant drop of water so they can surf on it - it turns out to be quite impressive, and they are even able to make it move!
We have Pinky and Perry teaming up to stop Doofenshmirtz.
Knot My Problem
Phineas, Ferb, and the other kids manage to untie most of their giant Gordian Knot without needing to resort to Cutting the Knot. Of course, Candace ends up eating it, but still...
Candace, with Irving's technical help, manages to completely record the audio version of a giant Fireside Girls book in only hours - a task which Isabella guessed would take her a week.
Phineas and Ferb and their friends climb into outer space on their rock climbing wall.
Doofenshmirtz throwing a hungry shark off himself, none the worse for wear.
In addition, how they broke status quo. Stacy takes a third option and covertly refuses to have her memory erased, then lies to Monogram's face.
The end of the episode, where Ferb successfully manages to get Phineas to have some alone time with Isabella by pretending that he had other things to do.
The derailed climax to the Trojan war reenactment, in which Ferb builds a laser-shooting, laser-proof wooden T. rex to assault the city, and Phineas eventually taking it down using flying chariots (but collapsing the entire castle along with it).
Buford casually sidestepping an incoming water balloon.
Phineas is the most laid-back guy you could ever hope to meet. Even when he has a lot of emotional investment in the idea for the day and everything goes horribly wrong, he, for the most part, maintains an upbeat, cheerful attitude. When the group is left with mere minutes before the sun goes down, Buford equips everyone with bikes to make a timely return possible. The only choice left for Candace is a tricycle, but Candace refuses to go on it. Phineas tries to persuade her in a reasonable, relaxed tone for a few moments. When she still refuses, Phineas snaps, possibly for the first time ever, and yells "GET ON THE TRIKE!" Candace is so intimidated that she scrambles onto the trike without a word. Doubles as a Crowning Moment of Funny.
After Doof meet up with Vanessa, Monogram finally decides to arrest Doof after all that's happened. Vanessa pulls out what appears to be a gun and demands they release him. They do so, and on their getaway she reveals it was just a hairdryer. Doof then realizes that she did something evil, and as a result is proud of her.
Buford's skepticism at the start of this episode was a Crowning Moment of Awesome, as it showed, without a doubt, that this episode was going to be truly special, as Phineas was finally being called on his ability to do anything.
Phineas managing to break out of his Heroic BSOD on the island, turning the giant map into a paper airplane, propelling themselves off two palm trees using a giant rubber band, breaking the damnSOUND BARRIER,and still managing to make it back to Danville before the sun sets.
The titular song, not just for being Awesome Music but also for being damn inspiring.
Phineas and Ferb Musical Cliptastic Countdown Hosted by Kelly Osbourne
Perry coming down from out of nowhere to stop Doofenshmirtz from zapping Kelly into another dimension.
Phineas and Ferb: Mission Marvel
When the fight against the villains in the mall ends in disaster and the heroes are on the verge of giving up hope, Perry (disguised as a platypus-themed superhero) pulls a Big Damn Heroes and gets them to safety.
Thor: Thank you, small but mighty friend.
Right before the penultimate battle, the depowered superheroes are easily curbstomped when they try to confront the villains. Iron Man is flung up high into the air while Red Skull taunts him about how he has neither powers nor allies left to help him. Cue Big Damn Heroes from Hulkjeet (in a Shout-Out to The Avengers!), followed by Phineas and Ferb in the Beak suit and Perry. Oh, and Doofenshmirtz joins the fight too. Usingwaffles.
Doofenshmirtz's involvement is especially awesome considering that Red Skull dismissed his waffle-inator (among others) as being useless earlier in the special. It's not. His intervention frees three of the captured superheroes and continues to trip up the villains several times during the following battle.
The game of Keep Away as the heroes prevent the villains from getting the reactor core. Finally, the superheroes get to show what they are made of even without their powers, going from Brought Down to Normal to Brought Down to Badass. Highlights include Spiderman temporarily taking down three villains in quick succession using golf equipment, Hulk and Thor putting a bicycle and a skateboard to good use, and Buford joining the fray wielding nothing but a fish. Also noteworthy is that 70% of the characters fighting on the heroes' side are handicapped in some waynote The superheroes from their lack of powers, Phineas and Ferb from the Beak suit only being partly functional, and Buford by virtue of having neither powers nor high-tech equipment, yet they still keep it up long enough for Candace and Isabella to save the day (keep reading for that one).
Candace and Isabella putting two and two together and realizing that the superheroes' powers must have been converted to data inside the kids' space station. Later, they crash the spaceship down to Earth (albeit by accident) onto the villains before they can repower their machine, bringing back the superheroes' powers at the same time.
At last, when the superheroes' powers are returned, they simply tell the kids to sit back and watch for this one. They then pose with an Avengers-esque pan shot and proceed to unleash a massive Curb-Stomp Battle on the villains. Perry getting to fight alongside them like a true blue superhero is the icing on the cake.
The fact that the creators worked very hard to ensure that the crossover would not violate Marvel canon. It's somewhat telling that the most contentious characterization from the special turned out to that of Phineas rather than any of the Marvel characters. In addition, the fact that Disney apparently liked the crossover so much they essentially okayed a Star Wars crossover right away.