Some of the songs such as Come Home, Perry or You Snuck Your Way Right Into My Heart definitely count.
Actually, the entire show is a great Crowning Moment of Heartwarming... Think about it, the fact that this is a mixed family is a non-issue entirely. And by design of the creators, no one is a complete jerk or an idiot. (Except Suzy.)
Well, not even Suzy, if you think about it. It's pretty clear that the only two people she's consistently mean to are Buford, the bully of the series, and Candace, who she views as a rival for her brother's affections. It's not exactly a redeeming trait, especially since all we really see of Suzy is scenes of her being unnecessarily cruel to Candace, but it's still at least understandable to some degree.
Turns out Suzy's only horrible to people when Jeremy's nearby, since it allows her to manipulate him into doing what she wants him to do. When she's off the clock, she and Candace actually hit it off pretty well. It's kinda cute in a sick, twisted way.
In fact, in the episode where we find this fact out ('Suddenly Suzy'), she actually coaches Candace how to not only get her way, but to get her brothers to bust themselves!Granted, it doesn't work, but still...
Just about anytime Phineas and Ferb use their inventions and skills to help others out, not just to have fun. Shows that even at their young age, they don't have to be useless all the time. In "The Doonkelberry Imperative", they even brilliantly come up with a solution to make peace within Druselstein and allow doonkelberries to be exported from there once more. (Unfortunately, the peace only lasts until the Druselsteinians decide to name a day after Phineas and Ferb and find that they cannot agree on what to call it.)
Phineas constantly naming their creations or big ideas after Ferb. Considering how much Ferb is sort of unnoticed by everyone*
Candance showing more affection towards Phineas, Candance usually just screaming for Phineas when she's in mortal peril, no one giving him any credit to being the lower half of the Beak. It's not really intentional as his quietness makes him somewhat easy to overlook and Ferb isn't really the attention type anyway but one does feel injustice for him
, it really says how much Phineas loves Ferb. It's almost as if he's saying "See this gigantic this we built today? Named after Ferb. Don't you dare overlook him!!" with every creation named after his green-haired step-brother.
Season 1
Rollercoaster
After the rollercoaster ride is over, we get this exchange:
Isabella: It really was the coolest coaster ever. You guys make a great team.
Phineas: Well, a brother is a brother. But I couldn't have asked for a better one than Ferb. You know what I mean?
Made extra sweet when you consider the fact that they're only stepbrothers, but they're just too good of friends to really care about that.
Flop Starz
Jeremy encouraging Candace to sing onstage, as well as Candace actually getting into the song and realizing for a few moments that her brothers aren't the nuisances she'd thought they were after all. Then it's cut short pretty abruptly by Phineas announcing it's their last show...
Candace Loses Her Head
Candace is exasperated to see what her brothers are up to this time as usual, when it turns out they remodeled Mt. Rushmore to include a bust of Candace. Candace's face goes from shock to teary-eyed joy.
And then she frantically tries to show it to her mom — not to try to bust her brothers as usual, but to show her what a beautiful job they did.
It's a Mud, Mud, Mud, Mud World
It's brief, but after Candace wins the monster truck rally, her (step)dad hugs her and says he's very proud of her. Aww...
Mom's Birthday
Candace is trying to do something special for Linda's birthday, but at first, Phineas and Ferb (unintentionally) show her up (she tried to deliver breakfast in bed, they had an omelet station). Then, Doofenshmirtz's latest scheme ruins her plan to get Mom a sundress (moths eat it) and play a song she wrote (all her instruments are shrunken into nothingness). Phineas and Ferb's final gift was a video tribute to their Mom, ending with footage of Candace practicing the song... which leads Candace, Phineas, and Ferb to go on stage and perform together. Awwwww...
When Candace slips into her parents' bedroom to try to give her mom a birthday breakfast in bed, we see that Linda is sleeping with a picture of Lawrence while he's out of town. Totally cute, and massive amounts of awwwww...
What? No mention that this is the first time Candace pets Perry? Considering how she usually insults him in several episodes later.
Candace:Oh, hey, Perry. (With a smile, she knells down to pet him) Where have you been? You missed all the fun.
Perry:(chatters)
Journey to the Center of Candace
Doofenshmirtz builds a device that will kill anybody that can't make up their mind. Immediately, Perry has a flashback to earlier that morning, when Phineas and Ferb couldn't make up their minds about that day's project. Less than ten seconds later, he has Doof shackled to a pipe and is calling in backup. It just shows how much Perry loves his owners.
Dude, We're Getting the Band Back Together
Lawrence forgets his and Linda's wedding anniversary. When he tells their kids about the time they first kissed at a concert, they decide to surprise their parents by getting the band back together to do a special concert for them. The scene of Linda and Lawrence kissing at the end is very touching — as is the fact that all three kids worked together on it, when Candace is usually the antagonist.
Dr. Doofenshmirtz tries to throw his teenage daughter Vanessa a birthday party, but she flies into a rage because he secretly invited all her Goth friends to a party designed for a five-year-old girl. (Something he has apparently done every year previous, to her great annoyance.) When Doofenshmirtz accidentally destroys everything (and gets blown up himself), Vanessa shows appreciation for what he did for her because it ends up making the party better. A bit of a Broken Aesop if you think about it, but still kind of touching.
The end of the episode is just so sweet.
A small CMOH also borders on Tear Jerker: Danny has just finished telling Phineas that nobody remembers his band any more. Cue the screaming crowds, and an expression of shock on Danny's face as he realizes that not only are they not forgotten other by this one couple, they are still loved by hundreds if not thousands of people. (The Tear Jerker is due to Fridge Logic; Danny honestly believes they have been forgotten and has just seemingly watched his hopes of a reunion dashed by the same infighting that broke up the band in the first place.)
The Best Lazy Day Ever
This episode has one of the most twisted, strangest CMOHs in the history of the show (whether it qualifies as one or not is questionable, as it's probably unintentional). When Candace finds out her brothers aren't doing any big project for the day, she is initially relieved that she can finally go about her personal business. However, it becomes clear busting her brothers is all she really does and all that really defines her. Then she starts to tear up (out of a personal identity crisis), realizing this fact. In its own insane way (similar to "Phineas and Ferb Get Busted"), you could say she finds out how important her brothers (and their crazy projects) are to her.
Candace: I can't do anything unless I'm trying to bust them for doing something. And if they're doing nothing, then (Psycho Strings play, and Candace starts crying)who-o-o i-is Ca-a-andace?
Voyage to the Bottom of Buford
The song that plays when Buford thinks of the fun he has had with Biff is a real toucher. Just watch it and tell me that doesn't make you cry tears of happiness.
Traffic Cam Caper
The boys spend the episode helping Candace retrieve a security camera DVD that's been stolen from them by Perry, with help from Norm the Robot (It Makes Sense in Context). When Phineas manages to get the disc, he jumps and ends up hanging onto the drawbridge that Norm slipped off of, and drops the disc right on the edge of the bridge. Unfortunately for him, he's got his hands in an oil slick that Norm left behind and is gonna fall off that bridge unless something is done. Candace thinks hard, looking at both choices of what she has to save here, before pulling Phineas up right when he's about to fall into the river. When he shows surprise at the fact that she didn't save the disc, she hugs him and replies "And let you fall? You may be a pain, but you are my brother."
One Good Scare Ought to Do It!
The reason Isabella isn't scared by the haunted house is because she's holding Phineas' hand. It's Fridge Brilliance mixed with CMoH.
Also, she tells Candace it was great because she had a day's undivided attention from him.
When the B PlotCleanup Crew arrives and Phineas winds up nearly falling to his death, Isabella not only rallies the Fireside Girls to make an impromptu trampoline with their sashes, she manages to catch him when he bounces off... and her crush nearly getting killed has been the only thing scary enough for the whole episode to get rid of those blasted hiccups. And then there's how long he stayed in her arms...
The Monster of Phineas-n-Ferbenstein
A brief one when Dr. Phineastein says that he and Ferbgor will never lose the platypus monster they created again. We even get a shot of the monster tearing up!
"Oh well, win some lose some, buddy. You'll always be the number one monster in my book!"
Oil on Candace
Django's painting and his father's reaction to it at the end of the episode.
"Thank you, Perry the Platypus. Thank you."
Out to Launch
The scene when Candace is trapped in a spaceship that is stuck in a decaying orbit and the boys are coaching her through the process of escaping, most notably "Just relax and take Ferb's hand."
When the boys thank Candace for saving them from Doof's space station and jump starting their ship.
Phineas: Ferb and I just wanted to say thank you. We were in a pretty precarious situation back there, and if it wasn't for your bravery, who knows what would'a happened?
Candace actually manages to get Mom to see what Phineas and Ferb are doing — in this case, putting plane wings on the family car so it can fly, and building a giant tower on which to park it (which then falls on the garage) — so Mom sends the boys to a hellish reform school. At first, Candace is ecstatic to have them out of her hair, but she soon grows to miss her brothers so much that she, along with Jeremy, embarks on a rescue mission to bust them out of there. Granted, the whole thing turns out to be All Just a Dreamwithin a dream that Perry is having, but it's this particular episode that really shows you that, deep down inside, Candace loves her brothers very much and doesn't know what she'd do without them.
Perry waking up from his dream in the end. It's a small thing, but his little smile at realizing that his cover hasn't been blown and his family hasn't been taken away from him is really sweet.
During the dream-within-a-dream, Perry and Doof's unseen B-plot saves the Flynn-Fletcher kids and Jeremy from the Smile Away general...or whatever he's called. You just know that Perry steered the unknown inator in that direction to keep his family safe.
Mom forgiving Candace for interrupting her all those other times to see the unseen things that Phineas and Ferb were doing and knowing that Candace was telling the truth all those times and she wasn't crazy.
Candace's pleading-while-crying to Phineas and Ferb in that episode about how their creativity isn't bad, but the best thing about them and how she regrets ever having them shipped off to that reformatory school in the first place easily has the capability to bring a viewer to tears.
It's kind of sweet to look back and realize that Perry was dreaming (within a dream) about Candace getting over her busting obsession/getting along with the boys. And, by the same measure, that he saved them, even at the cost of his secret identity.
Season 2
The Lake Nose Monster
A bystander lampshades Ferb's Once an Episode line and then proclaims it to be boring, upon which Phineas turns to Ferb and reassures him, "I didn't think it was boring."
Candace agreeing (however reluctantly: "I'm gonna have to do the right thing here, aren't I?") to dispose of the evidence she found and help keep Nosey's existence a secret.
Phineas and Ferb being the first humans ever to befriend Nosey and earn his trust.
Don't Even Blink
The lack of interaction between Candace and Ferb has already been noted on the Tear Jerker page... but it's worth mentioning that, due to this, the smaller exchanges are made much more adorable. Ferb's line of dialogue at this episode's end was a brief allusion to quantum theory and was largely Played for Laughs - but that didn't stop it from coming across as rather consoling, in the face of another failure.
Candace showing her brothers how to take care of "Perry's" egg. Too bad it backfires on her at the end of the episode. (Even when she does something nice, she can't seem to catch a break, can she?)
Ferb putting a handkerchief on the egg when Phineas mentioned it was getting cold. Doubles as a Crowning Moment of Funny.
Gaming the System
Candace has just defeated the final boss using her own health bar. Unfortunately, as the massive foe stumbles backwards off the edge, he crushes Phineas and Ferb with his foot. After staring in shock at them for about two seconds, Candace rushes over, drops to her knees and cradles Phineas in her arms just before him and Ferb de-pixelate. She then throws back her head and lets out completely devastated "'''NOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO!'''" before breaking down in tears. Of course, since this is a video game, the boys only lost a life. It's a rather unusual way of showing it, but it's proof that she really does love them and would be heartbroken if she lost them.
The Chronicles of Meap
Phineas's "Cute Tracker" burning out when it's reset to stop ignoring Isabella is strangely adorable.
Thaddeus and Thor
It was largely out of her own competitiveness, but there's Candace sticking up for her brothers. She even has her mom go back the grocery store so they wouldn't get busted (until the competition was over, at least).
Perry comforting Doofenshmirtz after he loses the kickball game.
Vanessa cheering for Doof during the game (even if she didn't actually think he'd do well).
Oh, There You Are, Perry
The ending, as pictured above.
It may be a blink-and-you'll-miss-it moment, but when Dr. Doofenshmirtz takes up a (temporary) job working for another supervillain and there's a picture of Vanessa visible on his desk. D'awww.
Not to mention he probably tries so hard to be a good dad because of how abusive his parents were. Just goes to show he's not really a totally bad guy underneath it all.
Perry switches between Phineas's and Ferb's beds in the middle of the night to be fair to both of them, which is adorable. (It might also explain why he ends up in Candace's bed quite a lot as well...)
The Baljeatles
Jeremy explaining to Candace that he hasn't nicknamed her because he likes her name just the way it is.
Phineas and Ferb's Quantum Boogaloo
"The stone age was once the future, as was the middle ages. Creativity and inventions never end!" That sums up the spirit of the show so well, especially now that we've actually seen versions of Phineas and Ferb in the Stone Age and the Middle Ages who had the exact same attitudes.
Finding Mary McGuffin
Doofenshmirtz reveals that he spent the better part of a decade relentlessly hunting down a Mary McGuffin doll for Vanessa, just because she told him that he would be the world's greatest dad if he did. Added onto that is Vanessa's reaction; she obviously has a very low opinion of Doofenshmirtz and considers herself too old for dolls, but she still accepts the gift and gives it a place of honor in her room.
Doofenshmirtz: I may be an evil scientist, but it doesn't take a degree purchased from the internet with your ex-wife's money to know how special and important you are to me.
The fact that she actually rips the doll out of a little girl's hands and walks away, leaving the girl crying, is strangely touching. It probably helps that the very next scene implies that Vanessa and Dr. D are starting to bond thanks to the incident.
This moment actually causes her to realize that maybe he's not so bad a dad after all, remembering all the moments where he actually pulled through as a parent, despite being completely embarrassing.
Nerdy Dancin'
The ending, where Candace tells Jeremy that it doesn't matter if he's a good dancer or not, she just wanted to have fun with him.
This is probably one of the most overlooked Heartwarming moments on the show, but the fact that Phineas and Ferb are willing to help Jeremy cheat on a dance show to make their sister proud. Awww!
Candace's Big Day
Candace has a total woobie moment when she bursts into tears telling her aunt Tiana that she ruined the wedding she was planning for her because she thought everything Phineas and Ferb did was terrible and the cake was a mish-mash of different foods with a live chicken in the bottom, all with her hair and makeup in a mess until Tiana tells Candace she loved everything and that she planned the perfect wedding for her.
I Was a Middle-Aged Robot
Candace and Dad enters a father-daughter wacky games competition, only to have Dad lose his memory and need to be replaced by the robotic duplicate Carl made "in case of emergency". The real Dad comes back at the end, feeling hopelessly confused but determined to jump into the potato sack race — and win. The hug they share at the end is simply precious.
Undercover Carl
When Monogram thinks Carl is in danger, he seems genuinely worried and comes to his rescue. This is especially sweet after you've seen how he normally treats Carl.
Invasion of the Ferb Snatchers
Despite the zany overtones, this episode can come across as quite heartwarming. After all, we usually hear Candace screeching about how she's going to bust the boys and, failing that, she usually only screams for Phineas when she's in trouble or worried (this can even be viewed as soon as "Ain't No Kiddie Ride", which is paired with "Invasion"), so it's definitely smile-worthy to see her concern for her step-brother, too.
Candace settling down with her brothers and watching a movie marathon with them. This is honestly one of the few interactions Candace has with them that does not involve busting.
The episode provided definite proof that, during the times Candace is not trying to get her brothers in trouble, their relationship to each other is very friendly.
Ain't No Kiddie Ride
Ferb being the one to save Candace's life is both this and awesome. He even shows his shock and fright for a moment when he sees Candace in danger.
Phineas and Ferb-Busters!
Norm "accidentally" spilling coffee on his replacement to save Doofenshmirtz counts both as this and a Crowning Moment of Awesome, especially considering the fact that Doofenshmirtz didn't really care about Norm until that point.
Norm: There was no rug, sir.
The Lizard Whisperer
It's brief, but during Ferb's completely epic and out-of-character speech, he, Phineas, and Isabella all share a side-to-side hug.
Actually, it's not out of character so much as it is a more direct demonstration of what is usually more subtly implied in the show: even though Phineas is the frontman and is usually given most of the credit, Ferb's the backbone and the heart to the group of kids, even though he hardly speaks!
It's a blink-and-you-miss-it, but a photo of Candace can be seen in Jeremy's guitar case. Daww.
The Lemonade Stand
Candace cancels a trip to the mall with Stacy to bust her brothers. Stacy gets mad and "breaks up" with Candace. At the end, Candace decides not to bust Phineas and Ferb's lemonade stand and apologizes to Stacy. It's all summed up in this song
Buford of all people being the one to sympathize with Candace was strangely heartwarming as well.
Nerds of a Feather
Candace spends most of the episode dressed as Ducky Mo-Mo, which she doesn't want anyone to know about. At the end Candace reveals her identity, which earns her sound dissing. Jeremy, however, thinks Ducky Mo-Mo isn't so lame after all. Suzy runs up to her, thinking she's Ducky Mo-Mo and says "I love you, Ducky Mo-Mo!" Candace's reply: "And Ducky Mo-Mo loves you," complete with hugs. Awwwwwww!
Candace's whole Ducky Momo side story is one for people who have trouble giving up things they liked as kids and are children at heart.
When Albert said "Brother!" and helped Irving. Albert begins 'casting his spell,' and then Irving (still in his robot costume) joins him. Then they both go "Brother!" and continuing chanting the spell to fight the 'monster.'
Wizard of Odd
The ending, when Candace has woken up from her dream and sees Phineas, Ferb, and co. in a giant unicycle. Phineas asks if she wants to have fun with them. As she is about to try to bust them, she says, "Did you say fun?" and Ferb tells her that the most fun can be found "in their own backyard". And she sits in the unicycle next to Jeremy. As they ride off, Phineas pulls down the screen and says, "Have fun, everybody!"
Ladies and Gentlemen, Meet Max Modem!
Lawrence loves Linda so much that he's willing to let Phineas and Ferb turn him into 80s One Hit Wonder "Max Modem" just because he's insecure that she'll prefer her glitzy Lindana lifestyle to a quiet life with him. Linda's reaction to realizing that Max Modem is Lawrence is also very sweet.
Brain Drain
The ending, where Vanessa finally considers Doof to be cool.
Perry helping his nemesis out, despite all the humiliation Doof put him through in the episode, by using the machine to make Doof bust some mad tunes on the turntable. After playing through a good chunk of his tune Doof looks down where Perry was and... he's not there, he's behind Doof and simply smiles and gives him a thumbs-up before leaving, and it turns out that Heinz was DJing by himself most of the time after Perry got him going.
Make Play
Young Heinz, thoughtfully giving his mother a teddy bear he won spending a year of allowance despite everything he had been put through. Turns into a Tear Jerker when she turns right around and gives it to his brother Roger.
Season 3
Run, Candace, Run
The scene where Anabelle is reunited with her family. Sure, she's a one-time character that we barely know anything about, but it's still adorably sweet.
Phineas' Birthday Clip-O-Rama!
Candace, after stealing the DVD of the boys' inventions at Buford's house, narrowly manages to come home with it. As she's about to show it to Linda, Phineas gives a big thank you to everyone in the yard, telling them that he's a really lucky guy to have such great friends and family, making Candace get all teary. She sobs out that she simply can't bust them, not on Phineas' birthday, and smashes the DVD. As it turns out, the wrench she smashed the DVD with is exactly what Phineas wanted for a birthday present. He then tells her how amazing a sister she is, and they tearfully hug. How sweet.
It's also one of the longest, yet least tedious hugs ever shared on television. (14 whole seconds)
Phineas's speech is this in itself. Get ready to get chokey:
Phineas: I just have to say, I'm a lucky guy. I mean, so far this has been a rockin' great summer. I've sure had a lot of fun. But it's not about satisfying your personal desires. It's about all of you. Being surrounded by the best family and the best friends anyone could hope to have. All the people I love, and who love me right back. Today was a great day; the best day ever.
And, despite how badly Candace tends to treat him:
Phineas: Aw, Candace, you're a great person. Why, if I had a nickel for every time you've done something nice for me... well, I wouldn't know what to do with that much money!
A small one when Phineas and Ferb replace Candace's dried out lamb cobbler with some of their moon-made ice cream.
Magic Carpet Ride
This moment of sheer adorable:
Ferb:(standing on top of the TV, arms spread out, as the rug flies) Does anyone else want to be king of the world?
Phineas:(leaning on the TV with a satisfied smile) Eh, keep it, bro. It suits you.
Doubles as Fridge Brilliance when you realize that Ferb just might become the President. Maybe.
We find out that as a kid, Doof had a painting ruined by Roger. So later, he tries to get revenge when he shows a painting during a mayor thing. But as Doof about to use his Stain inator, it's revealed to be...Doof's painting, which roger felt bad for ruining. After all the horrible things Roger has caused for Doof, this is sweet. ... Of course Doof's painting is stained again, but by then it doesn't matter.
One line from Lawrence at the end of the musical number: "Oh, thank you boys, this was lovely." Especially sweet since the boys build the flying carpet to cheer him up.
Phineas and Ferb Interrupted
Everyone pitching in to help Phineas and Ferb return to their old selves after they were accidentally hit by the Dull-and-boring-inator. (Okay, Candace probably did it mostly so she could have the chance to bust them, while Doofenshmirtz wasn't even aware of their plight and thought Perry was helping him, but it was still nice to see everyone working together like that.)
Mommy Can You Hear Me?
The ending, where Ferb finally manages to give their astronaut friend a Happy Birthday message. Granted the scene is done as one big shout out to the movie 2001: A Space Odyssey and seeing Ferb as a glowing fetus would freak out smaller children, but its the thought that counts.
Doofenshmirtz using his Amusing Injuries to save his daughter and her friends. Literally, he sacrifices himself by getting stung by hundreds of bees to save them.
"YOU LEAVE MY BABY GIRL ALONE!"
"So Candace, did you have fun with your brothers today?" "(Beat) Yes. Yes I did."
My Fair Goalie
Part of the extended Fletcher family gets on Ferb's case about whether or not he's still a 'true Brit', and Phineas wastes no time in sticking up for him, even though Baljeet and Buford unintentionally make that several times harder. Later in the episode - after we've been informed of a truly bizarre curseinvolving emus - Phineas goes on to provide us with this:
Phineas: Don't worry you guys, if I know my brother, he'll come through for us!
Not even the Bait and Switch that directly follows puts a damper on it, particularly since it precedes this:
Phineas: Ferb! You came to play!
Ferb: As long as my team will have me, curse and all.
Phineas: Of course we will! It's not about winning, it's about the joy of the game!
Ferb's last line during the credits.
Actually, lads, I'm not a Brit or a Yank. I'm just Ferb.
Jeremy and Candace's bit towards the end. Specially because it finally reveals what was Unrevealed by the start of the season. Jeremy likes Candace because of the way she is, including crazy busting.
Perry placing a blanket on a sick Doofenshmirtz as he sleeps. Awww.
Bullseye!
For an episode that was based on Rule of Funny - that even called itself out on coming close to breaking Willing Suspension of Disbelief - this one had an awfully sweet ending. All it took was one glance at his sons and Lawrence— who had been hit by the Turn-Everything-Evil-inator/izer— went back to being his usual Adorkable self before even 30 seconds had passed. No "I Know You're in There Somewhere" Fight required.
Over the course of the episode, you'll see Perry breathe a sigh of relief at least five times. This might seem excessive for a fifteen minute segment, but it also means that he was holding his breath for a good portion of the episode. Perry, the super secret agent with 'nerves of steel' (and several other metal themed attributes), was just that scared of losing his family.
Not to mention, before Lawrence was zapped by the -inator, Perry was taking his time slowly cutting his way out of the trap he was being contained in. The moment things took a bad turn he pulled out his jetpack and blasted his way out of there.
That's the Spirit
At the climax, the boys end up hugging each other for reassurance. It's not just a quick 'Haha, that was scary!' thing, either - the camera cuts away and then cuts back and they're still latched onto one another. Awwww.
A Phineas and Ferb Family Christmas
Candace admitting that she enjoyed the Christmas special.
Linda: Hey, boys. I heard you were doing Christmas in July.
Candace: Yes, yes they were. And... and... it was actually really sweet.
Doof Dynasty
We get this brief but utterly adorable moment between Phineas and Isabella: After the boys make it to the dungeon that she's been confined in, instead of stepping away from the door so they can break in like she suggested they do, she bursts through the door and gives Phineas a massive tackle hug while saying "My hero!". Made even sweeter if you recall, earlier in the episode, that this Ancient-Chinese version of Phineas actuall does show signs of liking her.
This◊ blink-and-you'll-miss-it moment right afterwards seals it.
Gi-Ants
In "Gi-Ants", Phineas and Ferb build a giant ant farm. In order to go inside, they need to spray themselves, Isabella, Buford, and Baljeet in ant pheromones. When their friends agree and go inside the ant farm, Phineas turns to Ferb and says "You know what I like about our friends? We say things like 'We're gonna spray you with ant pheromones' and they're like 'Okay, whatever'. They're so cool." This is a kid who builds amazing machines and rides everyday, and yet he considers his (more) ordinary friends to be cool.
Perry The Actorpus
The boys get to spend the day with Perry, and even get a musical number for it. It's so nice just seeing the three having fun together and playing around for a change.
Candace taking part in an Alcoholics Anonymous-like group in regards to busting brothers, which is headed by Mandy, Candace's rival from "Thaddeus and Thor". Toward the end, Candace actually makes progress, and Mandy happily hugs her in congratulations.
Bully Bromance Breakup
Even with a bully-sized hole in your heart, pretty much the entire Buford/Baljeet plot is sure to warm it to 1200 degrees.
Buford(to Doofenshmirtz, referring to Baljeet): There comes a time when you don’t wanna bully everyone. You just wanna bully someone you love.
Even thought he eventually comes to regret it, Baljeet being so happy after freeing himself from Buford's bullying that he's dancing around and singing is guaranteed to at least make you grin.
When Phineas was having trouble coping with not being able to invent anything, we have Ferb showing concern, including a moment with him putting his hand on Phineas' shoulder.
The Doonkelberry Imperative
Perry opts to stay and keep Doof company throughout the dangerous Druselstein driving test. Dr. D even comments on how Perry makes him feel safer during their stay in Druselstein. The whole thing is very heartwarming in its own way.
"*Sniff* Hold my hand, Perry the platypus. I'm scared..."
Balloony, having become one of Mitch's henchmen, remembers its past with Doofenshmirtz and turns on the robot army swarming Doof, taking down all of them but making a Heroic Sacrificein the process.
Perry "reviving" Balloony and bringing it back to Doofenshmirtz, as well as the montage that follows.
When Phineas falls under Mitch's new cuteness, Isabella manages to snap him out of it through her cuteness. He then explains that she is basically cute on the inside as well as the outside. Things are nice and sweet until Phineas states that it is a scientific fact.
Although even with Phineas stating it as a scientific fact, it's still nice and sweet, with Phineas saying Isabella is cute yet again in his own way. Now if only Isabella would kiss him already, the one thing proven to break his obliviousness...
Candace sacrificing her phone, along with all of the evidence of the "bust-worthy" adventure they just had, in order to stop Mitch.
The song in which all the, um, Meap-like species is gearing up for battle, not really heartwarming, but really cute.
The Mom Attractor
Candace asks Lawrence what Linda likes, and he gets the idea to make his famous Rhubarb Creme Brulee that she likes. At the end, the titular attractor disappears, leaving only Lawrence and the Creme Brulee...
Linda: Whose idea was this?
Lawrence: Actually, it was Candace's idea.
Linda: Honey, you are awesome.
Lawrence briefly recalling that he used to make said Creme Brulee for her all the time when they were dating was pretty adorable.
You really gotta love Phineas (and Vincent Martella) when Candace is doing her "I'm awesome" dance, and Phineas just looks at Ferb and agrees...
Phineas: Candace is awesome. Awesome awesome aweSOME, awesome awesome aweSOME...
Doof comforting Vanessa after she breaks up with Johnny.
Doofenshmirtz creating a trap inspired by Vanessa's fashion style.
Sipping with the Enemy
Vanessa Doofenshmirtz actually sticks up for her father, referring to him as a "misunderstood genius."
Where's Perry?
After Perry pretends to be sick in order to stay behind from the vacation and stop Doof, the boys not only show immediate concern over him but offer to stay behind' from their vacation as well in order to make sure he's okay.
Monogram allowing Perry to go join his family rather than return to Danville on the jet.
The Candace robot sacrificing itself and giving Candace Jeremy's message - which revealed he didn't actually break up with her-before it "died."
Where's Perry? Where he feels is home, with Phineas and Ferb.
What does Perry use to redirect the -inator beam to turn Carl back to good? A framed photograph of Phineas and Ferb.
Given how often Candace suffers from (and complains about) the Animals Hate Her trope, seeing her befriend the local wildlife was a nice turn of events.
Ferb's relationship with his brother couldn't be summarized any simpler:
Baljeet: (After Phineas insists against all evidence that Perry needs their help)...We are in Africa.
Buford: Pretty much sums it up.
Ferb: Well, has he been wrong before?
When Worlds Collide
Buford's friendship with Tristan.
Road to Danville
Doofenshmirtz complains about how he is thirsty and that Perry isn't helping him while they are stranded in the desert, closing his eyes and wanting to see him gone. When he opens them, he sees that Perry has indeed left and storms off on his own. Moments later, Perry returns with a glass of water.
When Doofenshmirtz finally reaches the bus stop, he breaks down from not being allowed onboard (due to him not having any tickets)... then Perry catches up to him with two tickets. Doof is moved to the point of shedding a tear!
And when Perry is the one who gets rejected from the bus due to animals not being allowed, Doofenshmirtz eventually gets off the bus to find him, bringing back Perry's jetpack.
At the end, Perry helping Doofenshmirtz reach his play on time.
This Is Your Backstory
What causesEvil Monster Doofenshmirtz to turn back to normal? A set of photos of him and Perry together, which Perry keeps in his wallet.
The fact that Vanessa's arrival gave Doofenshmirtz so many happy memories that his inator nearly reset.
Season 4
Happy New Year!
Candace and Jeremy finally share another kiss after ages in "Happy New Year". Also Jeremy saying that he still likes Candace for who she is, even if she can't stop trying to bust Phineas and Ferb.
The song "It's a New Year" has a nice atmosphere to it, with everyone being happy and enjoying themselves.
On a rather shippy note, Phineas and Isabella dancing.
This quote from Ferb:
"'Auld lang syne' literally means 'old long ago'. But I'd rather think of New Years as an unspoiled universe."
Fly On the Wall
A small one when Candace finally returns home after enduring countless dangers as a fly. Baljeet takes notice of her and informs the gang. When Phineas realizes that someone must have been tampering with their daily invention and had ultimately put Candace in danger, Phineas takes on an alarmingly dangerous tone of voice when he says, "Buford...?" narrowing his eyes as he does so. It's a very small moment but it's heartwarming in the sense that we get to see Phineas's more protective side and love for his sister.
Candace thanking her brothers over and over after being returned to normal (despite her backtracking in between and threatening to bust them as usual).
Perry helping Doofenshmirtz get over his "evil scientist's block".
My Sweet Ride
Candace allowing Phineas and Ferb keep the trophy their car won.
Also her reaction to the car.
Candace: You guys are so... AWESOME!
In a meta sense, the fact that the car doesn't disappear at the end of the episode, implying that Candace actually gets to keep something nice for once.
Sidetracked
The Ocean's Eleven-inspired ending scene, with Perry, Lyla, Doofenshmirtz, Monogram, Carl, and Peter the Panda at Niagara Falls, is rather touching.
The way Perry smiles and jumps into Phineas's lap at the end is adorable.
Primal Perry
Doofenshmirtz has been unable to recognize Perry without his hat... again... and calling him "Steven the Platypus." When Perry gets his hat back at the end, Doof is upset at not being able to say goodbye to "Steven," so Perry distracts him and hides his hat, allowing Doof to say his goodbyes.
Mind Share
Candace's concern and determination to get her brothers' (and their friends') minds back in their bodies before the mind share platform self-destructs.
Specials and Miscellaneous
Phineas and Ferb Christmas Vacation!
The entire last ten minutes. Including, but not limited to, Buford's Christmas wish: for his friends to think of him as a nice guy.
That includes the end credits, especially the song.
Buford going through Danville and having everyone turn their lights on to restore Christmas. Also Clewn't manually designating Buford as "nice" after Buford's nice deed.
"That Christmas Feeling".
Phineas and Ferb Summer Belongs to You!
Candace, Jeremy, Paris. They actually use the G- and B- words with each other.
Jeremy coming home early to kiss Candace.
Doofenshmirtz seeing that Vanessa might be a tiny bit evil, after stopping him from getting arrested by Monogram.
His eyes well up in tears... of pride. Aww!
It's a subtle one, but when Candace was singing her bit in the song "Summer Belongs To You", she ruffles Ferb's hair cutely. It so "Aaaawwwwww!"-inducing because Candace and Ferb are just stepsiblings and that that was practically the only time where they interact as brother and sister.
Especially the half-of-a-second bit where Ferb smiles after Candace did so.
What she sings makes it better. Not only is she proud of them but she thought it was merely implausible at the beginning of the journey that they would do the undoable. That's a lot of faith in their skill.
I traveled halfway 'round the world and almost turned and ran away
But you helped me get my courage back, so now I've got to say
That, though I've often thought of you as just a nuisance and a bother
Today I can't imagine having better little brothers!
And you gotta believe in something, so today I believed in you!
And you came through! We made it! I've never been so proud!
I know at first it seemed implausible
But we accomplished the impossible
Now there's something that I have to say out loud
Time is what you make of it, so take a chance!
Life is full of music, so you oughta dance!
The world's a stage and it is time for your debut!
Don't waste a minute sitting on that chair!
The world is calling so, just get out there!
You can see forever so your dreams are all in view!
The entire scene with Isabella pulling Phineas out of his Heroic BSOD is just aww-inducing, and quickly followed by a Crowning Moment of Funny when she almost lets slip of her crush on him.
Ferb's one-sentence pep talk to Vanessa about her dad is fairly sweet. Not to mention what happens after that with the flower. I really hope we get more of it in future episodes.
Likewise, Ferb's "talk" with Isabella on the beach was sort of touching, given that a) the two rarely interact with each other, and b) it contains a bit of Fridge Brilliance when you remember Ferb's experiences in Paris mirrored her own.
Buford giving everybody back their bikes so they can get home before sundown, mixed with Crowning Moment of Awesome.
Moreso when you realize that Buford genuinely wanted an adventure where they truly and undeniably proved that they could do anything they set before them and that summer really belonged to them - he only made a high-stakes bet so Phineas wouldn't have the option to not go through with everything. (And so he could eat a bug.)
Phineas and Ferb's pep talk for Candace when she's freaking out about her relationship with Jeremy. A heartwarming talk with a stealth math joke.
Candace: Well, my summer's been a series of failures. I have a hard time believing in anything.
Phineas: Well, you got on this plane. You know, back when it was a plane. Which means you believed in us.
Ferb: And we believe in you.
Phineas: And therefore, through the transitive property of belief, you DO believe in yourself.
Made all the better by "I Believe We Can" playing during the scene.
Other
This interview with Wired Magazine in which they discuss one of the show's most heartwarming features:
Phineas has a habit of announcing brightly, "I know what we’re going to do today!" For Bart Simpson, that would mean a prank phone call to Moe’s Tavern; for the South Park slackers, a stream of V-Chipped obscenities (at the least). "The easiest place to go for humor is characters saying mean things to each other," says one of the show’s creators, Dan Povenmire. "But we wanted them to be genuinely nice with each other and still have some edge."
The Phineas and Ferb 3D online video game "Transport-inators of Doom!" when you stop to think about it. You're playing the protective big brother who searches for/rescues his younger brother. Perry helping separately is endearing too.
