During Mr. Robinson's stellar performance, an old man leans over to his friend and asks "Whoa, who is this guy?" and Rocky, Mr. Robinson's son tells him "That's my dad. Rock on dude!"
In "The Responsible", Gumball decides to take the rap for Anais flooding the house. She's so touched she hugged him and whispered "thank you". But when Gumball was about to say it, he sees his mom's eyes are on fire, so he blames it on Darwin.
The ending of "The Quest", right up to where Tina's dad comes up from behind Anais, Gumball, and Darwin.
After getting falsely arrested for robbing a convenience store in "The Spoon", Nicole still has her family celebrating her birthday with them besides her cell. The cops found her innocent after all, too.
If you think about it, Alan and Carmen's relationship is this. Carmen is a cactus and Alan is a balloon, but that doesn't stop them from loving each other, and attempting to kiss each other.
The end of "The Painting", where Anais asserts that, even though the drawing she made showed her father as lazy, her mother as stressed-out, and her brothers as destructive, it says "I love my family" and she meant it.
Anais: If you'd listened for a second, you'd know have known that I never wanted anyone to change.
Mom: But I thought you were unhappy, honey. That painting?
Heck, the whole ending is, when Nicole realizes she should never have tried to suppress her husband's spirit and returns his cape.
"The Cottontail Cavalier has returned!"
Darwin comforting Gumball after he suffers a panic attack in "The Prank"... at least until it gets a little too Ho Yay.
In "The Picnic", Darwin saves Gumball from the nasty creatures of the forest.
Nobody messes with my team! (Darwin then fish-slaps one of the creatures, forcing all of them to run away!)
In "The Mustache", Richard bought those male supplements that his kids ate by accident because he was intimidated by the internet ads. Nicole hugs him and says she loves him for who he his, and so do his kids. Given Richard's personality and the fact that he felt he was unnattractive, it felt really sweet to hear his family say that about him.
The end of "The Meddler".
Gumball: Mom, you know how I said I wanted to be my own man and make my own decisions?
Gumball: Can it just wait for a few years?
Nicole: The longer the better honey. Even when you're 80 you'll still be my Gummy-puss.
The end of "The Fight" when Tina and Gumball become friends.
At the end of "The Helmet", Darwin and Anais successfully persuading Gumball to get rid of his lucky hat made out of tinfoil to save him from falling into the garbage crusher when he tries to retrieve it. But it's what Anais says to him that really makes it a CMOH:
Anais: Gumball, we're nothing without you.
Darwin kissing Carrie in the Halloween Special. Instead of being offended, she just blushed.
What makes it all the more endearing is the Fridge Logic behind it. Being a ghost and having no physical form, Carrie's interactions with the world around her is limited, with many objects usually passing right through her unless they were ghostly objects. Darwin giving her a kiss after he and Gumball turned into ghosts themselves is most likely a first for her.
And in the same episode, Gumball apologizing to Anais.
The Wattersons enjoying the star that Richard accidentally purchased with all their savings 12 years ago in "The Treasure".
Gumball and Darwin trying to get in trouble so Principal Brown wouldn't have to break up with Miss Simian in "The Apology".
And Miss Simian finding out they weren't trouble makers and apologizing at the end.
"The Hero"..... that's all that needs to be said. Watch it, now.
For a more meta example, take a look at the main page quote from the creator of the show. It's rather sweet that he's found a home for all these discarded characters.
Gumball and Penny's relationship in general is really heartwarming, early on they questioned whether the other liked them too shy to hang out, to Gumball saving Penny from accidentally being run over by her own father (Extra points for being dressed as a knight), Gumball's speech on how when they're together it's like time/the universe stops just for them, the aforementioned Penny standing up for him when he was embarrassed. Pretty much everything that has to do with their relationship is adorable and heartwarming.
From "The World", there's a truly heartwarming montage of Anais playing with her Daisy the Donkey toy until the doll starts talking to her.