In "One Stayed Clean." If you watch closely this episode parodies Saving Private Ryan with Gus' friends sacrificing themselves so that he will remain clean for picture day. Really. Replace words like playground with country and kindergarteners with enemy soldiers. Gus' friends' devotion and resolve to keep him clean shows how loyal they are. What really nails the tear-jerker moment in, when its only Gus and T.J. in a hole as their last means of sanctuary and shelter, is Randall playing Red River Valley on a harmonica as T.J. strengthens his resolve to protect Gus.
This piece of Fridge Logic (Or Fridge Horror): Because Gus has to move from town-to-town all the time (his dad's in the military), he's eventually going to leave the town the show is set in, and leave the best friends he's had in his life. It's heartbreaking when you think about it.
"The Great Can Drive": Mikey's Shaming the Mob when his friends and the Ashleys take the Thanksgiving can drive competition too seriously. (For context, the class that donates the most canned food receives a turkey dinner as a prize, and the class with the Ashleys has won several years in a row, demoralizing the other students). He's spent the episode as the Only Sane Man, and happily requesting cans from neighbors because Mikey points out that the point of the competition is to make sure those less fortunate can have a Thanksgiving meal. Then it turns out both classes are tied, and the woman who started the competition reveals she has one more can which she was going to give to the winner. Cue both classes fighting over the last can and Mikey screaming at them to stop. The skirmish leads to all the canned food getting destroyed, and Mikey calls everyone out for their pettiness before walking off in a huff. Everyone is so ashamed that they work together to collect more cans to feed the homeless and say the competition was stupid because Mikey was right; it wasn't about them.
"Outcast Ashley":
Although they're (usually) antagonists, Ashley A. getting kicked out of the Ashleys is sad in a way. These girls have been friends since preschool, and were kicking out their best friend just for forgetting to wear purple on the anniversary of the day they met. She might've done some bad things in the past (and in future episodes, as this was one of the early season two episodes), but you can't help but feel sorta bad for Ashley A. The part where they rip her 'A' necklace off and stomp on it, and then tear the head off her teddy bear backpack, is especially harsh.
There's also the fact that Ashley A. legitimately becomes nicer when befriending Gretchen. She starts taking an interest in science, helping Gretchen with her solar viewing camera, and learning that the world doesn't revolve around her. Rather than move on, the other Ashleys scheme to sabotage the friendship because they think that Ashley A. doesn't deserve to be happy. This eventually leads to the Ashleys accepting her back for saying at least Gretchen's solar camera wasn't shoes, and Ashley A. leaves Gretchen in the dust. Just, ouch.
Gretchen's heartbreak when the Ashleys accidentally break her solar viewing camera. The poor girl spent weeks preparing for the solar eclipse, and one moment of pettiness undid her dedication to a unique scientific phenomenon. Fortunately, the gang reveals they made an identical camera as an Apology Gift and invite her to take the first view.
Despite being one of the biggest jerks at Third Street School, Lawson's reaction to discovering that the leader of the pale kids, formerly known as Tiny Sedgewick willingly chose to hang out with geeks instead of him might make you pity the guy. Especially the way the discussion went down, Lawson's distraught implies that he and Tiny might have been friends or at least good acquaintances before he got injured. To find out that his old friend is not only okay, but knowingly rejected him for someone Lawson deemed uncool might be a big blow for him.
"Speedy, We Hardly Knew Ye".
The gang return after the weekend to see that the class hamster, Speedy, has died. Mikey first playfully taps the glass of Speedy's tank, only to get worried about the hamster just lying there. T.J. tries to say maybe he's just tired from eating croutons, but Gus notes the crouton bowl is full. Ms. Grotke tries to shoo the class away from the tank and lie that Speedy is probably meditating. Realization dawns on the class when Gretchen picks up Speedy and checks for a heartbeat, saying, "He's not meditating! He's, he's-" and Mikey responds, "Speedy's DEAD!"
Gretchen says she's trying to think of Speedy as just DNA. She admits, however, that he was special and more than a clump of fur and genetic code.
T.J. decides to ask all the kids to have a funeral for Speedy. Later, the high school football team, the bus driver, and even the mayor arrive at the funeral, because they also had Speedy as their class pet. King Bob finds out when T.J. asks for permission to bury the hamster in the fifth-grade territory and says, "I didn't even know he was sick!" Then he orders his men to give a funeral with pomp and circumstance, complete with playing Taps on the kazoo. It drives everyone to tears.
Spinelli's reaction of Denial and Bargaining. She's spent most of the episode saying that Speedy is just a hamster and is not worth all this fuss. Then she dives into the grave, admitting she loved Speedy and wants to be buried with him.
It's then revealed that every time Speedy dies, he (and in some cases, she) is replaced with a new hamster without anyone knowing. Everyone's upset because they realize that the Speedy who just died wasn't the Speedy they remember, so T.J. gives them a speech on how it doesn't matter which Speedy belonged to who; it was that Speedy was always a great friend to them.
The montage of all the past Speedys. Especially the first clip of an early Speedy being cuddled by a boy hiding under his desk during one of the "Duck and Cover" exercises in the 1950's during the early days of the Cold War.
Gelman's bullying towards Gus in "Gus's Last Stand". Especially hard for someone who's been bullied heavily.
Then comes Gus's plan: To fight Gelman. It goes as well as expected, but the sad part is when Gus tells the other that is his plan. In his words, the worst Gelman can do is beat him up, and after that, "there's nothing to be scared of". The idea that a fourth grader thinks of that plan is saddening to think him getting beaten up is the only way to not be scared anymore of a bully.
Spinelli getting bullied endlessly in "Mama's Girl" after accidentally calling Miss Grotke "mama". It starts out somewhat humorous, but it gets to the point where she's afraid to go to school because of the bullying.
And Miss Grotke's speech about how bullying can really hurt someone, though the tears that flow will be of the "Amen to that" variety (if such a thing exists).
In "More Like Gretchen", after Spinelli's parents compare Spinelli to Gretchen and inadvertently make the latter feel inferior, she becomes so angry that she tells Gretchen that they're no longer friends. And Gretchen didn't even know what she was doing wrong—she was just being herself.
In "Weekend at Muriel's", we have Ms. Finster's reaction to overhearing Spinelli call her "boring".
Notably, Finster doesn't mind that Spinelli called her "mean" before the boring part, because she's the recess monitor, the kids HAVE to think she's mean, or the whole playground will devolve into anarchy, but boring? She remembers being a young troublemaker just like her charges, and suddenly, she's old and tired and boring, and she hadn't even noticed.
Just the thought of what would have happened had the gang been split up after the breaking of that statue in "Biggest Trouble Ever". Spinelli and Vince would have let their more negative traits get the best of them without TJ to balance them out, Gretchen would have skipped out elementary, middle and maybe even high school and had no friends and Mikey and Gus might not even have survived until high school. Only TJ would have made it out okay... and that's almost worse!
The way Ms. Finster reacts to Principal Prickly's promotion in "Prickly is Leaving" is very sad to watch. Especially when she tells the main six that she refuses to do anything that might disuade him from leaving because she cares about him and wants him to be happy.
It's even worse when we're introduced to his replacement, Dr. Slicer, a Sadist Teacher who's such a monster even Philiam Benedict from The Movie absolutely pales in comparison, and keep in mind, Benedict was a psychotic madman who wanted to create a new Ice Age because he thought it'd raise test scores! Unlike Benedict, Slicer genuinely wants to make every students life a living hell on a personal level, and the student and faculty can't even protest, because it might cost Prickley his dream job, which he ends up giving up anyway once he realizes how miserable Third Street would be in Slicers hands.
Mikey discovering that Ms. Salamone is engaged in "The Voice" after developing feelings toward her is very sad to watch. The poor kid almost gave up singing after this.
At the end of the episode he sings "Nobody Knows the Troubles I've Seen" while gazing longingly at Ms. Salamone. It's hard to watch the scene without shedding a tear.
"Pharaoh Bob" is this when you think about it. King Bob becomes a bit shaken at the fact he'll be forgotten after he stops being King of the Playground so he forces the students to build a pyramid (and becoming a jerk in the process). After said pyramid is destroyed by the rain (due to it being made out of mud and not stone), he's confronted by Gretchen and laments how he simply wants to be remembered and not forgotten.
In the episode, "The Hypnotist", this applies to Principal Prickly bonding with T.J. and the Recess Gang. T.J. promises that Prickly, who preferred to go by the alias of "Petey" as he was hypnotized by accident and made to believe he was 6 years old, would always have friends as long as they were around. Prickly then went to go play on the swings, only for Vince to point out the problem with T.J.'s statement: Prickly is not a child, he only believes he is. Second problem: because Prickly was no longer of sound mind, that would've made Ms. Finster the new principal in charge. They had to return Petey back to his old self, and as a result, lose their new friend.
The whole of "Bonky Fever" is sad. Mikey is turning ten, and his mom (who's apparently walked him to the bus stop and waited with him every day) tells him that now that he's getting older, he'll be going on his own. Mikey spirals into a deep depression that he copes with by reminiscing about Bonky, a singing, dancing dragon designed for preschoolers. His friends watch in horror as Mikey regresses further and further to a childlike state: he plays with Bonky toys made for little kids, carries around a hand puppet that he treats as a living thing, starts speaking like a baby, and even asks T.J. to help him to the bathroom. The final straw comes when his tenth birthday party is Bonky themed, with all of the kindergarteners attending, and Bonky "himself" appearing in a suit. The gang is forced to reveal the person in the costume—it's Mrs. Blumberg, who was trying to give her son what he wanted. Mikey runs out of the house, and she pursues him; this leads to one of the most earnest, frank, and generally heartbreaking conversations about growing up ever recorded on kids' TV. Mikey confesses that he knew his obsession with Bonky was childish but was so afraid of losing his mother and drifting away from her that he tried to recapture his lost youth. Mrs. Blumberg then admits that their bond will never quite be the same, but promises that she'll always be in his heart. The entire thing is a bittersweet meditation on getting older, how our parents are human beings, too, and that childhood is something that inevitably has to end.
The final shots of the episode pack in even more Tear Jerker moments. Mikey walks to the bus by himself, takes a deep breath, and climbs aboard, sitting next to Gus...and then the camera pans to reveal Mrs. Blumberg hiding behind a tree, where she was watching her little boy in case he needed her. The episode ends with her clearly choking back tears as she walks away.
The episode "The Legend of Big Kid" ends on a surprisingly sad note. T.J. is ambushed and captured by the kindergarteners, and over time, he gradually regresses into one of them. While his friends do rescue him in the end, T.J. admits that there was something wonderful about remembering the joys of being an innocent, carefree child, unafraid to nap or finger paint however he wanted. Gretchen points out that every kindergartener will eventually grow up, which is treated as a fate to be mourned, rather than celebrated.
In "That Stinking Feeling," Spinelli finds herself having a first crush, and everyone relentlessly teases her for it. She feels like a total outcast...and that's when Miss Finster sits down next to her and offers some advice—people may not expect "tough girls" like them to have emotions, but they do, and it's OK. Miss Finster even shares her own painful experience with love, saying that "Even if he does leave you in Paris with no money and a broken axle on the VW, in the end it's all worth it." The thought of Miss Finster being abandoned in a foreign country by a man she clearly cared for is painful, especially considering that it was decades ago and she hasn't forgotten about it.
"Yes Mikey Santa Does Shave"
Principal Prickly has a hard time getting Mikey to sing. Then he brings up the events of "The Voice". Mikey smiles sadly when remembering his teacher before launching into his trademark singing voice to do the Santa laugh.
Mikey is trying to prove to his friends that Santa is real only to be let down every time, first by a mall-Santa, then by Fitzhugh in the Christmas Parade, and finally by a radio DJ pretending to be Santa, once he discovers the truth he's absolutely crushed to the point where he no longer has any Christmas spirit and refuses to play Santa in the play. Though fortunately an old man encourages him to still believe and he comes to his senses.
His friends' reactions throughout this journey. At first, they go This Is Gonna Suck when Mikey asks them point-blank if they believe in Santa. Rather than lying, they try to break it to him gently that a man visiting every house at night is physically impossible. As Mikey insists that Santa is real and takes them through town to prove it, their expressions go from exasperation to worry. After the radio DJ disappoints Mikey, Gus tries to reassure him that there's still the pageant and he will be a great Santa. Mikey refuses to do the pageant and tears up his letter to Santa, walking away in a funk. Gretchen goes My God, What Have I Done? and quietly says, "Now I know how the Grinch must feel" because they broke Mikey.
