Blythe's friend Sue admires Blythe a lot and in episode 7 she comes off as a Stalker with a Crush towards Blythe by copying everything she does, right down to the shampoo.
Penny and Pepper go on quasi-dates in "Penny For Your Laughs". At least in Pepper's mind, that is.
Sunil and Vinnie seem very close to some viewers. In "Blythe's Big Adventure Part Two", during the fashion show, Vinnie helps Sunil out in showcasing one of his magic tricks, probably due to Sunil's huge Performance Anxiety. After Sunil saves the day in "Gailbreak", Vinnie comes up to him and gives him a big hug, and in "Russell Up Some Fun", they team up to prank Russell while giggling like a bunch of girls, and Sunil laughs heartily about Vinnie's Incredibly Lame Puns afterwards.
At the end of "Lights, Camera, Mongoose!", Vinnie goes to check if Sunil's alright (like he did with Penny earlier). Sunil is so happy about being back in Littlest Pet Shop, he pulls Vinnie close and their noses◊ bump together◊.
In the same episode, Vinnie basically had a mancrush on Shahrukh, another mongoose that looks very similar to Sunil.
Take a sip everytime Sunil and Vinnie cling to each other for safety in "Door-Jammed". They also do a Thriller parody where the two are in place of Michael Jackson and his girlfriend. Finally, it is also interesting to note that they accused all the other pets of being werewolves... but not each other. They also seem to spend time watching horror movies together.
Sunil's Imagine Spot of being a doctor and operating on Vinnie (who lost his tail) goes from him playing real music instruments in the operation room (which results Vinnie into getting a peacock tailof all things), to Russell, Minka and an overjoyed Vinnie fawning over him. Watch it here.
In "Eight Arms to Hold You" the two embrace each other out of reflex, notice and awkwardly let go of each other. During the episode Vinnie also keeps falling on Sunil as a Running Gag. When Sunil falls on Vinnie one time, he's happy things are "finally going his way".
Minor example; In one part of "Eight Arms to Hold You" Vinnie asks Sunil to "rendezvous" in the hall at night to crash Blythe's party together. Sunil asks him about the meaning of rendezvous, and Vinnie acts perplexed. Since it can't be that he didn't know the meaning of the word as he used it in the correct context, did he realize the romantic connotation the word can carry?
In "Heart of Parkness", Vinnie appears to be one worrying the most about when Sunil got lost in the park. Since he volunteers to be the lookout on the boat, hoping he can spot Sunil.
In "A Day at the Museum" Sunil and Vinnie get excited about watching a horror movie together. The being touchy with each other and hugging in fear from "Door-Jammed" makes a come-back.
In "Blythe's Big Idea" they are taking a bath and goofing off in a tiny tub of soap water together. For the Pet Jet fantasy, they are seated next to each other just like a couple would be and hug once again in fright when they suspect they are going to crash.
In "Commercial Success", they are sitting on the same chair while watching Jasper's commercial.
In "Shanghai Hi-Jinks" there's a brief scene at the start where Sunil pats Vinnie's head and affectionately calls him "sweet, ignorant Vinnie". Upon hearing they are going to Shanghai, Sunil lifts Vinnie up and swirls him around. At the end of the episode Sunil specifically goes to Vinnie, lifts him up again and hugs him, while praising him for his "colossal footwork" while dancing. None of the other pets do that with Vinnie. Their expressions really sell how much they like each other◊.
As of "Sunil's Sick Day", the writers aren't even hiding it anymore.
Zoe Trent and Pepper Clark basically have a lover's spat in "Dumb Dumbwaiter".
In "Frenemies", the two once again get into an argument on which party theme is suitable for Penny Ling. They make up by telling each other how great they think the other is.
In "Helicopter Dad", a scared Russell leaps into Vinnie's arms in Minka's Fantasy Sequence. In the same episode Minka's affection for Olive Shellstein resembles a crush.
In "Door-Jammed", Whittany and Blythe seem to get friendly fast after being stuck in the bathroom together, and it's revealed that Whittany actually likes Blythe a lot, she just treats her poorly because Brittany doesn't like Blythe.
It's questionable if this even counts as Ho Yay, because at this point it seems to be canon, but Vinnie's crush on Bruce the Iguana in "The Big Feathered Parade". Vinnie is completely infatuated with him, calls him his hero and daydreams about dancing with him on the parade while red flowers fall from the sky. Zoe even teases him about him having a "reptile crush" on Bruce, with Vinnie smiling after that comment.
In "A Day at the Museum" Minka and Penny Ling raise a baby dinosaur together and call it MinLing.
At the end of "Shanghai Hi-Jinks", Minka hugs and clings to Penny's face in her joy.
In "To Paris with Zoe", Madame Pom kisses Zoe numerous times on the cheeks upon reuniting with her.
Also when Zoe says she has a boyfriend, Madame Pom is shocked, she admits it's because she doesn't want Zoe to be distracted from the competition but it honestly looks like she feels threatened.