The episode where El Chavo is Mis-blamed for theft, ostracized by everyone and leaves temporarily. It traumatised several generations: seeing everyone calling him a thief at his face is pretty hard to watch. Made even better or worse by the ending: when El Chavo is cleared, he is talking to his friends about the time he spent away from the vecindad: he had gone to a church and, after being counseled by a priest, he decided to pray to God. Chilindrina and Quico assume he was praying for the thief to be caught, but Chavo instantly corrects them, saying he prayed for the culprit's reformation. The thief, Sr. Hurtado overhears this and is so touched that he has a Heel-Face Turn and not only returns everything he stole, but he also gets El Chavo a ham sandwich.
Another one is when Profesor Jirafales tells Don Ramon that he (Profesor Jirafales) truly loves teaching and genuinely wants the best for his obtuse pupils. The kids overhear this and they write on the blackboard: "We all love you sir!".
A double episode begins with El Chavo sleeping against Don Ramon's door because he had been promised to have breakfast and the kid didn't want to "let him run away with it" (it works, believe it). The two parts that compose this episode, despite hilarious, are filled with small moments of pure Tear Jerker.
El Chavo: (waiting for Chilindrina to bring the eggs for breakfast) Why is she taking so long...?
Don Ramón: Calm down. Can't you hold back hunger for five minutes?
El Chavo: (soul-crushingly slow) I've been holding it back for eight years...
Sr. Barriga: (after the breakfast eggs got broken and ruined) You mean that those eggs were for Chavo's breakfast?
Don Ramón: And mine too. For the whole week.
To make things even worse, the two-part episode ends up with El Chavo never getting his breakfast, and sleeping again against Don Ramón's door, hoping that, next morning, he may have a new chance. Cue sad background music, credits roll, and a box of napkins...
A great example comes from the episode right before the Beach Episode. By a series of events, every inhabitant of the Vecindad leaves to Acapulco. By the end of the episode, El Chavo is the only one around and we are greeted by some sad background music. Cue Sr. Barriga's arrival and, when he's told everyone is gone to Acapulco, he decides to go as well. He leaves, and when he's nearly gone, he stops, turns, and looks at El Chavo, alone in an empty Vecindad. Mr.Barriga tells him "Hey, Chavo... Want to go to Acapulco with me?", followed by Chavo's stuttering, hesitanty, soul-crushing reply: "M...Me...?"
Another one comes from a Christmas Episode. Señor Barriga gave all the boys a little toy truck as a present. Later, El Chavo disappears to return at the end of the episode. When everybody ask him were he went, he tells them that he gave his little truck to one of the neighbors' kid, while happily commenting they were going to believe it was left by Santa Claus. Surprised, all the others ask him why he gave up his toy to give it to the other boy he answers: "Well of course! Didn't you see he's a poor child?". Cue to all the others silently looking at the camera.
In the episode where the characters are looking at old photographs, we have the last conversation Doña Florinda had with her husband. It is played rather comedically, with him talking using Quico's maneirisms, like "Cala-te, cala-te!", which he says before he leaves to die in his job. Then, you realize that the last freaking thing he said to his wife was for he to shut up. You feel like a jackass for laughing at this scene right after that.
If we go to the tie-in books, we have El Chavo describing how nobody wanted to adopt him in the Orphanage of Fear, and by the end how El Chavo finds Jaimito the mailman dead in his apartmen, having passed away of old age. He at first can barely understand what happened, believing that he's just sleeping; then he realizes the truth and naively thinks "Well, Mr. Jaimito always said he was tired... now he can sleep and no one will disturb him, ever."
Thankfully the animated adaptation ignores that event and Jaimito is alive and well, still finding ways to avoid work
It does become a Heartwarming Moment when Chavo and Chilidrina end up seeing each other again after everyone one leaves and chuckle at the insanity of the situation before running into each other's arms, with Chilidrina in tears of happiness.
One can get a bit teary-eyed when learning how the relationships between Chespirito and his cast members became, especially with Carlos Villagrán due to rights over the characters. It does become less tearjerking after reading up that they all ended up on good terms.
The real life deaths of Ramon Valdez, who played Don Ramon (who was arguably the most popular character in the show); the show continued, but it was never the same without him.
The same could be said for the passings of Horacio Gómez Bolaños (Chespirito's brother, who played Godinez), Angelines Fernández (Doña Clotilde "la Bruja del 71"), and Raúl 'Chato' Padilla (Jaimito the cartero).
Of course, the death of Chespirito himself in 2014 may be the ultimate tearjerker, and probably makes all of the series' sad moments worse, but is heartwarming to know his legacy will remain alive for many generations to come.