Before the show even starts, the theme music is heartwarming in its own way. It's the kind of uplifting music that lets you know the Autobots will always protect the earth. Hear the full version here.
Consider that it doesn't really play until the credits roll (full movie version). The Autobots go through a lot in that five-part opener: the death of a friend and comrade (which hits Arcee hardest), destroying the space bridge linked to Cybertron, and the knowledge that the Decepticons are still out there (and Megatron's probably still out there)... but despite all this turmoil, they've found the strength to move on and continue fighting the good fight, because they have something to fight for.
Miko hugging Bulkhead (his finger anyway) when he comes back fine after the final battle in the pilot.
Jack's concern for Arcee, when she is almost killed at the end of "Darkness Rising".
Arcee (weakly): Jack... really? There are other motorcycles in the world. Jack: But you're my first.
The normally stoic Optimus offering to bring Raf a snowball back from the Arctic in "Scrapheap".
Prime holding Arcee's hand when they thought they were about to freeze to death.
Even when he's on the very verge of death, literally stumbling to reach the Groundbridge, when Optimus sees the swarm of Scraplets heading towards him and Arcee, he immediately places himself in front of her without hesitation.
Arcee allowing Jack to take Sierra for a ride at the end of "Speed Metal".
Arcee calling Jack "partner" after a huge battle with Airachnid in "Predatory". The sun rising helps.
Raf explaining that Bumblebee is like family to him in "Out of his head". Ratchet seemed to smile at this, to give you an idea.
In the same episode, when Raf tells Ratchet not to leave him in the base before going after Bee, saying "He needs me." Ratchet, ever the snarker, responds with a exasperated "of course he does". But there's a slight smile on his face when he says it.
In it's own totally bizarre way, Bulkhead rescuing Breakdown from MECH in "Operation Breakdown" was oddly heartwarming.
Jack reconciling things with his mom, and introducing Arcee to her for the first time.
In "Rock Bottom", Miko trying to dig herself and Bulkhead out of the cave while Bulkhead holds up the ceiling initially comes off as rather cute. However, when Miko starts running out of air to breathe, her insistence on continuing even as she's risking her life really shows how much she cares about the big guy.
More Tear Jerker material as Starscream arrives and threatens the two... Bulkhead tells Miko to run, but she just shakes her head and hugs his foot. Then Jack arrives in the drill vehicle and Bulkhead tells her again to get out of there... and she's in tears as she finally gives in and grabs Jack's hand.
Starscream having Soundwave record him while he talks about how he has decided to give up on his ambition to become leader of the Decepticons might count. Considering the fact that Soundwave and Starscream, while civil for the most part, don't see eye to eye for obviousreasons, and the fact that Soundwave technically doesn't even have to record it, it's somewhat touching that he would do that for Starscream. Even more so when you remember what Starscream tells Soundwave afterward.
Starscream: Thank you for listening, Soundwave.
The Autobots saving Raf's life.
Ratchet admitting that he has grown to like Raf. It shows he's not as much of a jerk as he first seemed.
Miko hugging Raf might be small, but it shows that she cares for her friends.
Optimus' little smile to Raf when they were both recovering was adorable.
June and Jack hugging in "One Shall Rise, Part One". It shows she acknowledges that the Autobots save lives. She does ground him for nine years, however.
"One Shall Rise, Part Two": Bulkhead, Arcee, and Bumblebee all vowing to protect humanity for the sake of their human friends.
Optimus entrusting Jack with the key to the ground bridge power supply before entering Unicron. Their talk in and of itself is great, with Optimus himself acknowledging that Jack has matured enough and earned his trust.
Without spoiling anything, one scene of episode 26 makes it even more heartwarming.
A slightly less notable scene due to all the action and fast paced story is when Ratchet immediately shields the kids in the building when a serious earthquake hits. Fowler and June are left out in the cold, but Ratchet can't stretch that far (and it's later revealed that they moved to join the kids anyway).
When Ratchet is describing Megatron and Optimus' past, there's a scene where Megatronus and Orion Pax are standing next to each other while smiling on a vibrant Cybertron. How once, Megatron had the ability to care.
Jack suits up and heads out to Cybertron. The "goodbye and good luck" bit between him and the group really shows how close they've all become.
In what has got to be some of the most hilariousMood Whiplash ever, a Star WarsShout-Out leads to one for Breakdown, of all bots. After reading what he believes to be a Vehicon (actually Fowler) the riot act for missing a check-in, Fowler repeats Han Solo's famous "How are you?" line. Breakdown is initially taken off-guard, then tells Fowler that he knows they're doing a thankless job and encourages him to keep up the good work.
The following exchange from "Orion Pax, Part 3".
Optimus Prime: Hello, Rafael.
Then there's Jack using a fully-charged Key to Vector Sigma to restore Orion Pax's memories as Optimus Prime.
Orion Pax:(Sees the Key in Jack's hand) Are you... certain I am worthy?
Jack: You have no idea.
Easy to miss, but as Jack and the bots return to base, Raf runs up to Bumblebee and gives his foot a big hug. D'aawwwww!
In the "Orion Pax" three-parter, we witness the Character Development of June from an overprotective mother-hen into a parent who trusts and has faith in her child Jack. What mother wouldn't be proud of watching her son grow into a brave warrior and responsible adult before her eyes?
When Ratchet picks Raf up from school in "Operation Bumblebee, Part 1", he sees that the boy is upset and offers to let him ride with the siren on. Raf declines, but it was a nice gesture, all the same. (Also counts as a funny moment.)
Ratchet also does a good job of comforting a self-deprecating Optimus, telling him not to take Megatron's words about what he may have done while he had amnesia seriously.
The lengths Ratchet is willing to go to to help Bumblebee. He immediately and without hesitation offers to donate his own T-Cog to Bumblebee when retrieving Bumblebee's own T-Cog doesn't look possible any time soon. He ends up not having to do so, but he got as far as being there on the operating table anesthetized so Arcee could perform the surgery in his place.
The reason why they don't follow through on the transplant after Bumblebee's cog is horrifically damaged: Bumblebee won't accept it.
And then there's Bumblebee's utter joy when Ratchet is able to successfully repair and reinstall his T-Cog, giving him back the ability to transform. The first thing he wants to do? Go out for a nice long ride with Raf.
Ratchet's delight is pretty palpable too, especially that first smile he gives.
Optimus and Wheeljack telling Dreadwing they'll gladly face destruction with Bulkhead, who currently had a bomb strapped to his chest. Autobots stick together until the end.
The fact that Bulkhead thought he was going to die and tried to keep Wheeljack away from him in an effort to save him.
Deep down, Bulkhead's just a big cuddly ball of heartwarming. This episode just brought it to the forefront. "Sorry, fishies!"
Near the beginning of "Nemesis Prime" we see Jack, Miko, and Raf racing toy cars with their guardians (Arcee, Bulkhead, and Bumblebee) cheering them on. Something's just really sweet about seeing these characters who are often in very serious situations have fun once in a while.
Plus the fact that Raf, the youngest and smallest by far, is handily kicking their asses.
In "Grill" Fowler speaks for the Autobots to his superiors and defends that they are willing to lay down their lives to protect Earth. He even states Optimus is like a true patriot, in which he refers to him likes he's an American hero.
Fowler compliments the kids too, calling them all selfless patriots, even Miko!
Optimus telling Arcee she was stronger for her choice in not killing Airachnid and instead trapping her in stasis. Shows just how proud of her he was.
Ratchet saving Jack in "Flying Mind". Anybody else could have got him, but Ratchet saves him anyway to make sure.
The end of "Triage" has Ratchet and Wheeljack earn the other one's respect. It might not seem like much, but considering it's Ratchet and Wheeljack, it says a lot.
Ratchet: I am glad... that I had you as backup, Wheeljack.
Wheeljack: See you around... Ratchet.
Ratchet's sheer joy at seeing Project Iacon data now flooding into the Autobot base.
"Rafael, you're a genius!"
Ratchet and Raf working together on the virus. It's just one more display of how much Ratchet has come to care for and respect the kid.
Soundwave gets one, as well. He's got Wheeljack at his mercy and is about to finish him off, but stops and flies off the moment he gets an S.O.S. from Laserbeak. It's actually kind of endearing that the silent bot would give up such an ideal opportunity to go help his drone.
"Toxicity". Bulkhead, seemingly ready to check out after being wounded by Hardshell and poisoned by Tox-En, gets back up and soldiers on after being reminded of one thing: Miko.
His interactions with Fowler are also heartwarming, especially when Fowler talks about his past as an army ranger and Bulkhead states that they're Not So Different.
Wheeljack warming up to Miko in "Hurt".
Oh, so much in "Hurt":
Agent Fowler: Keep me posted, Prime. *turns to leave* I mean it.
Miko's showing some signs of growing up.
Miko: I'm never leaving you again.
Wheeljack telling Miko how most Wreckers would be proud of her achievements. Though it doesn't seem to cheer her up.
"The Human Factor" gives us Bulkhead finally getting along with Smokescreen after the latter saves him from Breakdown!Silas. Smokescreen even mentions he studied every battle the Wreckers fought, causing Bulkhead to say "There's hope for you yet, newbie."
For that matter, Knock Out's reaction to Breakdown!Silas. He may be a bad guy, but he can still care.
He threatens to dissect the newcomer for doing just that to Breakdown, and seems extremely pleased when he is given permission to do so. If that doesn't show that he cared about his buddy, nothing does. It's nice... in a terrifying way.
Ratchet's response when Optimus orders him to hack the Damocles Kill Sat.
Ratchet: Without my backup? Without Rafael?
From "Legacy", Jack and Smokescreen have fun together, almost instantly forming a relationship that's akin to an easy older/younger brother dynamic (looking for Smoke's alt mode, getting back at Vince). Sure Jack was great to get Arcee to come back after Cliff died, but this was probably one of the rare times that Jack has had time to enjoy being with a bot. (aside from the ending of course)
Smokescreen being comforted by Bulkhead after Starscream steals the third key from right under their noses.
Arcee congratulating Smokescreen on his escape from the Nemesis (and retrieval of two Omega Keys) in "Inside Job".
Even better in that she first gives an exhasperated sigh, hands on hips, and then smiles as she does so. Of all of them, she was the one it took the longest to warm up to him, but the process is steadily visible over the course of each episode and completes itself here.
The ending of "Patch" and Dreadwing's general feelings towards his brother Skyquake shows that some Decepticons do have the ability care.
This troper is happy to have Starscream back with the Decepticons. It seems that he learned from his mistakes and realize where he belongs. Megatron allows him to serve at his side again, since it's better he's with him than against him. Whether or not Starscream plans to overthrow Megatron again remains to be seen, but in "Darkest Hour" he showed concern for his master after the Autobots destroyed the Omega Keys.
The begining of "Regeneration" has Dreadwing hand the Forge of Solus Prime over to the Autobots. After some hesitation, Optimus once again offers the noble Seeker a chance to change and become an Autobot. Dreadwing once again refuses, but declines far more politely than the last time Optimus made the offer.
The Proud Warrior made his peace with Prime, showing clear respect and gratitude to the Autobot Commander with words that summarize what he stands for better than any other:
"Betraying my kind is not the same as accepting yours."
Smokescreen trying to hand over the key he'd snagged to Optimus. Especially coming from someone Arcee had previously dubbed "Destiny's Child".
"Optimus, an honor like this shouldn't belong to me."
There's a very easy-to-miss, possibly unintentional one towards the end of the episode. When Megatron refers to the human children as the Autobots' "pets," Optimus Prime's eyes narrow slightly. It's as if he's saying, "Don't call them that."
"Darkest Hour". Despite what follows, Optimus readily and without hesitation destroys the Omega Lock, destroying any chance of a restored Cybertron, perhaps even dooming his own race, to save Earth from being cyberformed by Megatron, which would have wiped out all indigenous life.
Watch his expression - he actually stops in thought, and looks towards the kids, who are screaming in horror at their planet about to be cyberformed and everything they love being gone. Then he turns to the Decepticons, where Megatron, Starscream, Knock Out and even Soundwave are laughing about it, his eyes narrow in Tranquil Fury, and his resolve firmly sets in.
Wheeljack defending the other Autobots from the Decepticons, declaring that they're still all on the same team. It says something that a loose cannon like Jackie still considers Team Prime his family.
Wheeljack: We're still on the same team, Doc. Always will be.
Fowler defending the Autobots from the Decepticons.
The best part in my opinion was the exchange. When each Autobot hands over their key for one of the children each. Bulkhead gets Miko, and the pair throw an insult at Knock Out. Bumblebee gets Raf and, well we can't tell exactly what he told Soundwave but, it's doubtful that anybody needed a translation for that one. Then both Arcee and Smokescreen get Jack.
The last one was sort of forced by Megatron, though it's symbolic regardless. Jack and Smokescreen started to bond a few episodes back. It makes a truckload of sense.
Starscream's expression when he takes in the fact that Cybertron may be permanently dead shows that he does show some degree of concern for his home. He's basically heartbroken, something you wouldn't expect from someone like him.
Optimus Prime escapes the Decepticons' search through the wreckage of the base because Smokescreen refused to abandon him to face them alone. He went back for him (Phase Shifter and all).
Raf and Bumblebee try and fail to get things working on the Harbinger, and then... Ratchet's wordless "don't you dare touch that" warning has never been so good to hear.
The smile he gives Raf when he starts working on the Harbinger was also quite nice. Especially when we last saw him, he was on the verge of a Despair Event Horizon.
Pretty much all of the hugs in "Prey" qualify.
Later, when the rest of the gang shows up, Ratchet's "You're alive!" contains more undisguised joy than we usually see from the Autobot's resident Grumpy Old Man.
Just look at the reactions of Team Prime when Optimus returns to the fray. Especially from the kids.
While Optimus and Ultra Magnus are getting reacquainted, if you look very carefully you can see Magnus break out a full on smile. It literally only lasts for a split second, but it made Magnus seem really adorable.
Starscream, of all bots, gets one when he sees Megatron badly injured after Optimus Prime hurls him into Darkmount's power core. Instead of leaving him for dead (and indeed, Megatron refused aid), the Seeker orders Vehicons to rescue Megatron. Considering who we're talking about here, that's saying quite a bit.
Smokescreen has just used the Forge of Solus Prime to bring back Optimus Prime from the brink of Eyelights Out and is preparing himself for a What the Hell, Hero? speech from Ratchet, the bot who was most angry over the destruction of the Omega Lock. Instead, Ratchet pretty much says that dooming their home planet in exchange for Optimus' (and by extension, everybody else's) life was a worthy tradeoff.
Fowler congratulating Team Prime on their victory:
"On behalf of the President and the Joint Chiefs, I thank you all for your selfless heroism in defense of this planet. I'm only sorry that the world can't yet know of your undying dedication because I, for one, owe you my life, my liberty and my future." (salutes them)
Ultra Magnus giving up his command.
Ultra Magnus: Sir, I am honored to relinquish command of the Autobots to you. Optimus: Welcome to Earth, Ultra Magnus, and to Team Prime.
Nice little blink-and-you'll-miss-it, if you watch closely just before the end credits roll. You'll notice Ultra Magnus give Bulkhead a pat on the back. A very unexpected show of friendship from him.
Watching all of Team Prime stand proudly, side by side was probably the single most heartwarming moment in the entire series so far. And that's saying something!
It's even more so on a meta level: Ever since the Season 2 finale, the Autobots have been on the ropes. Now, for the first time in almost a year, an episode ended on one of the biggest high-notes of the series.
Arcee reflecting how Optimus Prime might not be with the team today if not for Smokescreen. It's especially heartwarming since, in various second season episodes, she chewed him out for being inexperienced and impulsive.
It's rather sweet that the Autobots let their human companions sleep in their base since Jasper's still in ruins.
Arcee giving Wheeljack relationship advice regarding his "dropout" last episode. It works well enough that he decides to stay on the team.
Wheeljack later commenting that Ultra Magnus "fought like a Wrecker."
Earlier in the episode, when they come across the Predacon clones, Wheeljack prompting asks for permission to blow up the lab, which Ultra Magnus responds that if will it keep the Predacons from trampling over humanity, go ahead. After all their differences, they find common ground on protecting the Earth from the Decepticons.
As Ultra Magnus recovers at the end of the episode:
Ultra Magnus: Optimus. When we spoke earlier... what could be greater than an army? Optimus: A human concept, one I have learned since coming to Earth: family.
Megatron of all 'bots reassuring Predaking as unique and a "miracle of science" after he tells his story of being a Fish Out of Temporal Water, as well as how hopeful the huge 'Con is when he sees that his time alone is almost over. It's ultimately subverted however when Megatron engineers the destruction of the Predacon clones and Predaking is left alone after all.
In "Minus One", Wheeljack seems almost protective of Ultra Magnus.
Like when he stood up to Ratchet on Magnus behalf.
Or when he used one of his swords to block an energy blast aimed at Magnus.
In "Synthesis", Ratchet distracts Knock Out by asking him to fetch a piece of lab equipment and then thanks him when it arrives. Knock Out's response? A somewhat surprised, but very sincere "you're welcome."
Good manners must be rare among Decepticons.
There's more. Before that, Shockwave did not once order Ratchet around in the lab: The two of them discuss their progress together regarding the project as if they had abolished the entire Bot/Con split and Shockwave readily acknowledges Ratchet as the leading expert on the matter. Ratchet even calls him "sir" in return. And we get a rare glimpse of Ratchet thinking. This is something that could have happened if the War for Cybertron had never occurred.
Optimus' smile when Ratchet manages to contact the Autobots.
In "Deadlock", Bumblebee's joy at his voicebox being restored by the Omega Lock's cybermatter. To make it even better, the cybermatter was created in part by Ratchet's synthetic energon formula. As Optimus put it:
"It would seem the old field medic made good after all".
Early in the episode, Ratchet, who was the most upset after Optimus was forced to destroy the Omega Lock at the end of the second season, is willing to allow it to be destroyed again to stop Megatron.
Later, Ratchet goes head-to-head with Shockwave to stop him from using the Lock to cyberform Earth.
The Autobots using the Decepticons' rebuilt Omega Lock to accomplish what they planned last season: restore Cybertron.
After Megatron shoots down Bumblebee, Optimus overcomes the horror of the loss, bellows in fury and beats Megatron into the ground in just a few savage seconds. It doesn't stick as Megatron collapses within reach of a lost weapon, but it shows how Optimus feels about losing yet another to the war.
Of all the 'Cons, it's Starscream who loses it when Megatron dies.
In an odd way, the fact that Shockwave pulls Starscream out of the fight and retreats after the above, telling him not to throw his life away. While the Scientist was likely doing it out of pragmatism, it's still kind of neat to see he's prepared to help out even Starscream despite their less then stellar relationship.
"Don't make me hunt you down." Most Heartwarming Call Back of the entire series.
Bumblebee finally makes Warrior Class, in an official ceremony on Cybertron just as he wanted it to be.
Smokescreen not only admitting that he was chosen by the Matrix to be the next Prime, but humbly telling Bumblebee that he'd probably be better suited for the job than himself.
Smokescreen: Predacon allies, you called it, Bee. And to think, Optimus almost passed down the Matrix to me.
Megatron's Heel-Face Turn, having learned first-hand how horrible he was after Unicron gave him a taste of his own medicine and even going so far as to disband the Decepticons.
After Optimus flies into Cybertron's core, granting Primus the ability to again give life to Cybertron. What looks like a million Sparks fly up out of the Well. It was a truly beautiful sight.
The best part? It's easy to guess just whose Sparks they were. So in a sense, we're getting to see Cliffjumper, Tailgate, Seaspray, Breakdown, Makeshift, Skyquake, and Dreadwing again!
And amongst all of them, one particular Spark, implied to belong to Optimus himself, briefly pauses before the group before flying off with the rest of them. "T'il all are one", indeed.
Just before Optimus is swallowed by the light of the core the corner of his mouth lifts in a smile, which this troper doesn't remember having seen from him at any point during the show.
Out of Canon
In a meta-example, during a panel at BotCon 2011, Josh Keaton (Jack's voice actor) admitted that he'd never owned an Optimus Prime toy growing up. Before the panel ended, someone had found him one (admittedly not a difficult task at a Transformers convention). Peter Cullen even signed it for him.
"You are Cybertron's mightiest heroes, and I've called you all together for one reason: the end of the world is here, and it's our job to stop it. The world is counting on us, and we will not fail. You are all heroes, but today... we are all Cybertronians."