The fact that Russell was initially terrified of modeling, but has since gradually started to like it and seems to be making a career out of it. If the show ever gets to the point where he becomes a famous pet model following in Zoe's paw steps, that would be adorable.
Although we never got to see Roger and his wife (Lauren) interact, due to her being long gone before the series began, it's obvious how much the two loved each other. It's even revealed in the season 4 final that Lauren told Roger that she could talk to pets.
Vinnie and Sunil's friendship is always heartwarming with just how close the two are despite being so different.
Olive finally coming out of her shell for Minka.
This whole scene with Roger and Blythe.
Roger: What are you doing in here?
Blythe: Being alone...
Roger: Isn't that what you wanted?
Blythe: I-I thought I did. Dad, I'm really sorry I yelled at you and told you to leave me alone.
Roger: It's okay. I guess I was pretty overbearing today. It's just that I feel bad when I'm away so much.
Blythe: And I totally miss you, but we don't need to be together every second to have fun.
Roger: You know what? You're right! Let's get out of here.
Blythe: *smiles* Okay.
Pepper and Zoe pointing out the best qualities in one another.
Zoe: Well... I guess I'd have to say that Pepper is.... Lucky.
Pepper: Lucky? How am I lucky?
Zoe: Cause you're so funny and have a lot of fun ideas and... That's why everyone likes you.
Penny Ling telling Zoe and Pepper that she loves both party ideas.
Blythe hugging Russell
Blythe: I think I'll miss you most of all.
Eight Arms to Hold You
Blythe letting Vinnie and Sunil stay at the sleepover.
Russell changing the game rules so everyone is a winner.
And no one's complaining.
Heart of Parkness
Sunil remembers all the good times with his friends.
Minka grooming Sunil
Sunil helping Zoe try on some new outfits
Sunil pretends to fall over to cheer up Vinnie after he messes up one of his dance moves.
Sunil making Penny laugh by tickling her
"The only thing that truly scared me, was the idea of not seeing all of you again."
When Steven the cobra returns, Sunil states he's absolutely willing to protect the other pets and Blythe from him "until [his] last breath". Let no-one ever doubt his devotion to his friends.
Blythe taking Sweet Cheeks to the park and just how happy he looks when he's finally allowed to have fun.
Despite how depressed it makes them, the fact that the pets change their personalities just to make Mrs. Twombly happy is really sweet of them.
What, Meme Worry?
Sunil being concerned for Vinnie when he thinks his friend is in pain. Turns into a Crowning Moment of Funny when it turns out Vinnie was faking it to mess with Sunil.
Jasper comforting Sunil when he's scared about getting his claws clipped is really sweet.
Pepper trying to keep jealous Zoe away from Sunil. Heartwarming because most of Pepper's interactions with Sunil have been her scaring or making fun of him. This is the first time she's actually stood up for him.
Zoe apologizing to Sunil for being jealous of him, and Sunil forgiving her with a hug.
Alligators and Handbags
Zoe finally snaps and tells Wiggles off for his bullying. Why? Because he made Penny Ling cry. You don't make Zoe's friends cry.
After Wiggles explains to the pets that he only acted scary because he thought that's how alligators were supposed to behave, the pets offer to be his first friends. They are later seen building a fort together.
Penny wiping Wiggles' tears away with her paw.
Blythe's Big IdeaCommercial Success
During the final commercial, Jasper keeps in Mrs. Twombly's poorly done scene solely to keep her happy.
The final commercial has the exact voices for the pets, just in the wrong bodies. The pets take it in good humor and enjoy it despite the mistake.
Blythe picking up Penny Ling when she arrives at the pet shop and welcomes her with a hug and belly rub.
To Paris With Zoe
Madame Pom and Zoe are very dear friends at this point, thinking back to the start of "Eve of Destruction" they were outright mortal enemies.
Penny Ling and the other pets all working together to make Sunil believe he's a super hero to help bring his confidence back.
Pepper and Captain Cuddles finally getting to talk and bond at the end of the episode.
Despite them not doing a very good job and almost ruining Pepper's chances with Cuddles, the other girls taking the time to give Pepper advice and making her look pretty shows what good friends all the pets are.
Buttercream realizing that Aunt Christie really does care about her after spending the whole episode thinking she doesn't.
Sunil hugging Vinnie and complimenting his "colossal footwork".
Penny realizing the other pets are just as much her family as her panda relatives are.
When watching for the first time, one could easily expect Penny Ling's relatives to snub her. But despite the fact that they are very different, they fully accept her.
Rodger was giving the Biskit twins actual attention and interacting with them in a fatherly way, it softened them turning them nice, and made them realize what "Real happiness" is for the first time. Later on, when he meets their father, Fisher, the two chum it up as if they were friends all their lives. Rodger is apparently just that charismatic.
Blythe playing Hide and Seek with the pets.
Penny befriending Mushroom.
Sunil's Sick Day
Vinnie and Sunil hugging at the end after apologizing to each other for their fight. Mrs. Twombly then tells Blythe that it's time for Vinnie to go home, and Vinnie is about to leave but then gives Sunil one last hug before he goes.
The flashback of Vinnie and Sunil playing in the bathtub and Vinnie helping Sunil when he accidentally swallows some bubbles.
Blythe's Pet Project
Pepper and Blythe introducing Shivers to his new, clean, clutter free home.
The Expo Factor part 1 and 2
Zoe helping Russell to be confident when having his picture taken. Just the gentle, reassuring tone she uses and how she teaches him some of her poses.
The butler getting a new job as a photographer and how happy he looks doing it.
The ending where all the pets get to be on the cover of the magazine.
The song the pets sing for Blythe to regain her confidence is probably the most heartwarming song in the entire show. Even more, this song makes you truly realize how far their friendship has evolved, compared to the first episode.
Lovesick Sunil in the "All Around The World" song after watching the song enough times, can cause one to start melting at simply how beyond happy he is.
Sugar Sprinkles' intentions. Despite how ironically it created less harmony than more (excluding Baabaloo), all she wanted to do was spread love.
The ferret finally finding her owner.
Sunil's speech to all the troubled animals, it even makes Vinnie cry.
Fish Out of Water
How kind Josh is to the chinchillas, even after he's fired from Largest Ever Pet Shop, he still wants to buy food for them.
If the Shoe Fits
The Biskits' butler sent invitations to Blythe and her friends.
The boy band is happy to sing the song Youngmee wrote for them.
The Very Littlest Pet Shop
Sunil comforting Vinnie.
The little girl telling Blythe that she misses Vinnie, or Princess Precious as she had named him, Vinnie hears this and gets teary eyed.
The Secret Recipe
Youngmee finding out Blythe can talk to animals, and totally accepts it (with flashback evidence), instead of thinking of her as a freak, or even insane.
Blythe's song "My Biggest Secret" has the pets welcoming Youngmee.
Winter Wonder Wha...? Snow Stormin' Back Window Room Enough Why Can't We Be Friends? Pet Sounds
The whole "If I Could Talk To The Humans" song
Proud as a... Peacock?
Pepper helping Basil boost his self-confidence.
Pepper standing up for Mitzi when the other pets are driving her to exhaustion.
Vinnie asks Mitzi to make the room smell like the sun. Instead of making him feel bad for his mistake, she tells him not to worry and that she knew what he meant.
In The Loop
Seeing the pets play together when they were younger.
Vinnie and Sunil have been best friends since they were little.
Russell using his time loop to spend time with the other pets so he could learn to understand them better.
It's The Pet Fest! part 1 and 2
In part 1 Blythe gives Mona Autumn a hug after she receives sponsorship from her. Mona doesn't mind at all.
The song in part 2 about how much humans and pets love each other.
Sweet Cheeks can be seen among the many pets at the Pet Fest, showing that his owner, Finola, is treating him with more care than the last time we saw them.
Minka tries to get Master Hop to teach her to be zen, but Master Hop is more interested in teaching Russell. After seeing how disappointed she is, Russell tells Master Hop that he refuses to be his student unless Minka joins them. The smile on Minka's face after hearing this is just adorable.