Nepeta Leijon

Nepeta is a young troll from the planet Alternia and one of Karkat Vantas' Greatest allies, also, she is feline... ya

Bikini Bottom Saga
Nepeta first appears in KVPS Chapter 2 alongside Kanaya Maryam on their home planet Alternia. The two are transported to Bikini Bottom by a rift opened up by Sandy Cheeks' invention, ending up inside her tree dome.

Nepeta is next seen defending Karkat from an attack by Mindy, buying him a chance to escape. During their scuffle, Mindy manages to incapacitate Nepeta, albeit barely.

Nepeta later joins Kanaya in cheering on Karkat during his battle with SpongeBob.

After the defeat of SpongeBob, the three trolls reunite once more. Nepeta and Kanaya inform Karkat of the situation regarding Kanaya's frozen heart in the Twilight Zone, and they agree to head to the Shadow Realm to find Mindy. Kanaya points out that Kevin had been listening in on their conversation, provoking his emergence from his hiding spot. After Kevin reveals that he has sent his fanbase after Karkat, Nepeta chases after him for a brief time before he is killed by an attack from Squidward's Board ability Superbad, which Nepeta herself narrowly avoids falling victim to.

Nepeta and Karkat team up to take on Squidward while Kanaya goes off to find them a ride. Nepeta manages to dodge Superbad's vines with ease, even managing to do so under fire. She keeps up the evasion until Squidward fires off bullets coated in Superbad's fatal ink, which spills upon Nepeta, seemingly killing her. It is then revealed that Nepeta's supposed death was all part of a gambit in which she used the vitamin-like nature of Superbad's ink to revive herself immediately after. She and Karkat then unleash a tag-team punch rush on Squidward, ending his life.

Shadow Realm Saga
After Squidward has been defeated, Nepeta, as well as Karkat and Kanaya, hitch a ride with the Risky Racer in search of a route to the Shadow Realm. However, their ride is cut short when they are stopped by Phineas, who gravely injures Karkat, rendering him unable to fight and leaving Nepeta alone to take him on.