The part at the end of DKC when Donkey and Diddy are at the treehouse having fun with each other is quite heartwarming.
Earlier, when they enter the banana hoard (that room that normally triggers the "failure" cutscene due to the entire stash of bananas being stolen) and they find their huge mountain of bananas returned to them.
When you 102% Donkey Kong Country 2, Cranky swallows his pride and admits he was wrong about Diddy not being cut out to be a game hero. He goes on to say he must take after himself and DK, subtly complimenting both of our favorite apes at once.
The ending of "Speed"; DK is apologizing to Candy that his duties to protect the island always seem to get in the way of their dates. Candy, however, assures him that it's no big deal in song.
"Sometimes I feel like I'm in the way / But I know he's out there, saving the day"
When Skurvy and Klump are reunited in the show.
The episode "Speak No Evil, Dude"; DK is given a Sadistic Choice where he has to either stop the entire island from being blown up or save Diddy by finding him an antidote for a life threatening disease. DK resolves to somehow do both because, to him, the island isn't worth living on without his little buddy.