In General

Coop and the S-Force's Odd Friendship: weird yet surprisingly adorable.
It's implied Coop's mom let Kiva stay with them and even join in (along with Jamie) on Thanksgiving Dinner with no fuss.

Season 1

All I Wanted Was A Slushie

Kiva's understandably exasperated with how Coop and Jamie care more about getting a slushy than helping her investigate an active threat. And doesn't try to hide it. But when Coop offers to pick her up some jerky, her mood, surprisingly, seems to ease up a bit and she happily accepts. Possibly the first hint of her actually starting to come around to them.
Later, she decides to try a slushie to see what all the fuss is, and finds it to her liking.

The Fat and the Furious

As a result of a broken key component, Coop is unable to use Megas immediately against the imminent Glorft attack. Fortunately Goat, Tiny and everyone else at the car show is willing to back him up. They're not always effective ("We're okay!"), but there's something charming about their successful attempt to stall the Glorft via car football, especially the expressions on their faces.
Coop and Tiny, despite being rivals at the car show, keep the competition between them friendly throughout the episode.
Kiva receiving a trophy for her repairing skills on Megas' CPU which was unanimously declared by the jury of the car show.
- And Coop admitting that she earned that win.
Whether it's canon or not is debateable, but the other members of Team Megas (plus Goat) grooving out on Megas' Manual Mode dance floor. Kiva, in particular, looks like she's having fun cutting loose.

DMV: Department of Megas Violations

Throughout the entire episode. Coop assumes that Darklos, the evil alien bounty hunter who's attacking Jersey City, is after him. It turns out that Darklos is actually trying to capture Kiva and extract her memories of the future for a bounty. After the gang defeats Darklos, Coop is depressed that she wasn't interested in him... so Kiva lies and tells him that the bounty hunter did want to capture him, as she'd heard about his incredible skills as a hero. Coop is genuinely thrilled, and it's one of the earliest times we see Kiva treat Coop with kindness.
The general friendliness that Darklos' kaiju mount displays once freed from her control is worth mentioning. The credits even reveal that Coop and the gang took him up on his offer to stop by!... If only to pester Darklos during her community service garbage collection job by tossing scraps of paper near her occassionally.

The Driver's Seat

After the two have been captured by the Glorft while attempting to save Coop, Jamie lays into Kiva about how he doesn't belong on these adventures and only comes along because Coop's his Only Friend... and Kiva's plan to save the future will separate the two for good. Kiva's response is to calmly break them out. Once reunited with Coop, Kiva explains to him how Jamie helped in the rescue attempt, and Jamie admits that Kiva did most of the work. Then they fistbump. Coop is utterly weirded out.

Don't Tell Mom the Babysitter's Coop

Coop's bratty, kid cousin coming to like spending time with the trio. Even begging his mom (to the trio's horror) to Coop babysit him more often.

S Force SOS

Seeing Kiva fully relaxed at the beach is this considering she constantly need to be focused on her job of training Coop.
Coop being more than happy to help rescue the S-Force, he clearly considers them some of his closest friends.

Space Booty

Kiva simultaneously explains to Coop and Jaime that Warlock had tried to have them both killed while her back was turned and tried to get her to leave the team. At this point all three give the space pirate a Death Glare as Kiva encourages Coop to beat Warlock and his men up, Coop is more than happy to oblige.
Coop: Listen you—
Kiva: (interjects) —arrogant overblown thief. You tried to break up our team, you almost killed Coop and Jamie, and you made me listen to your endless, cheesy pick-up lines!
Coop: Nice!

Rearview Mirror, Mirror Part 1

Alternate-reality Jamie from "Rearview Mirror-Mirror" imprisoned, insulted, and nearly killed Coop — but when he's in danger, Coop immediately shifts into "Save Jamie" gear and goes back for him.

Rearview Mirror, Mirror Part 2

Alternate Jamie showing concern for Coop when he's almost killed by Evil Coop. Especially considering Coop more or less caused the destruction of his army and stronghold.
Gorrath actually thought about making peace with Coop after defeating his evil alternate version, which Coop is receptive to it. Too bad Coop screwed it up by accidentally destroying Gorrath's army with their weapon.
Coop reuniting with his Jamie and Kiva at the end of the episode.