"Dawn Of The Eds." The Eds plan on sneaking into an R rated movie about killer robots when Ed starts recapping the story (...somehow) and they get so caught up in the moment that instead, they end up in the junkyard and play 'Space Outlaws' for the rest of the episode. Aside from basically being ten minutes of three friends just having fun, their Once an Episode scam doesn't hurt anyone (except Double D) and Ed even rescues Kevin from the Kanker sisters.
The ending of "A Fistful of Ed" where Eddy actually defends Edd from the Kankers, telling them to back off because he had a rough day. Eddy then acts shy about it and gives his friends hot dogs to shut them up. Eddy not only for the first time defended his best friend, but also subverted the Butt Monkey ending that they usually would get. It leaves me with a warm fuzzy feeling whenever I see it.
Eddy: (angrily) Everybody happy?!
Ed and Edd nod.
This goes double when you take into account that A Fistful of Ed aired near the tail end of the series. Despite all the crap the writers put them through, they let the series end on a high note to end all high notes.
This same episode also has Jimmy realizing that Edd is NOT the violent thug the other kids made him out to be since only a truly sensitive soul could crossbreed such a nice flower. Jimmy then decides to hear Double D's side of the story. Even more heartwarming? This was the same person who got all 3 of the Eds in trouble and got away with it. Now, he is kind, caring, and childish as usual.
I'm probably in the minority, but I thought Ed's misguided attempt at protecting his baby sister Sarah was adorable, even if it WAS against the innocent Double D.
The episode "See No Ed" where the kids (except Kevin) are worried about the Eds when they couldn't find them. Jimmy confesses that this was what he had wished for every birthday and feels guilty about it.
The Episode "Fa La La La Ed," where Ed brought the Christmas spirit in July, had this memorable exchange:
Double D: *weeping in shame* Jimmy: Double D? *holds out piggy bank* Merry Christmas. Double D: Why, thank you...but I couldn't. Jimmy: *pauses* But it's Christmas.
Also very moving, when Double D almost breaks Jimmy's piggy bank and is immediately remorseful:
In 'Duelin' Eds', Double D says he's going to make cupcakes for Eddy; Eddy's smile of appreciation is seen for a second before Rolf interrupts.
Probably a minor one, but in the flashback-episode 'Every Which Way But Ed', Nazz's flashback reveals that she used to be very overweight, and yet the flashback shows the other kids hanging out with her and everyone is completely nice and accepting towards her. I don't know if it's YMMV, but considering how mean people can be, I thought it was quite sweet.
Doubles as Heartwarming In Hindsight, but in It's Way Ed, after falling behind on the latest fads, Double D tries cheering Eddy up by pointing out that fads go in a cycle and that they'd be back in style. Ten years after that episode aired, The Movie premiered, and I think you can figure out what happens there.
'Dear Ed' ends in a typical manner: Johnny and Plank make up and Eddy still doesn't get any money. Before he can sulk about it though, he notices the music change with Jimmy and Ed dancing to it. Eddy seeths at first, but when Double Dee goes to join them, he pauses and decides that if you can't beat them, join them. The episode ends with the four of them dancing to disco music, completely forgetting what occurred no more than a minute ago. A nice and touching end compared to many other episodes.
Say what you want about Sarah, but her friendship and attentiveness towards Jimmy is actually rather sweet, especially considering how older characters (Kevin and Eddy in particular) are rather contemptous of him; Sarah's always there to stick up for her friend. Not to mention it's one of the rare occasions we see Sarah genuinely happy.
Double D being the Nice Guy he is in the Valentine's Day episode and, upon finding May Kanker sobbing in the Janitor's room because Ed rejected her and she has no Valentine's Day cards, quickly gives her a makeshift card to cheer her up, despite the fact normally the Kankers terrify the Eds. Aww...
Ed and Jimmy's bonding in "Ed In a Halfshell" was rather sweet, even though it did get ruined by the end of the episode.
"Momma's Little Ed": Eddy yells at Edd and throws him out of his room, but Ed's Puppy-Dog Eyes make him change his mind. So Eddy convinces Edd to come back and live with him (the scene is seen in the picture above).
A little Friendship Moment in "Ed or Tails": When Ed finally realizes that his two jawbreakers aren't enough for him and his two friends, he sadly but immediately gives them to Edd and Eddy.
"Tinker Ed": When Eddy (regardless of his real intentions) reassures Jimmy about the fairytales, Jimmy hugs the Eds and, for a moment, looks genuinely happy and innocent.