So here are a few things to note about the headcanon I use when dealing with Karkat. He’s a Troll, and trolls have different anatomy from humans, which I’ll explain here:-Trolls aren’t birthed, but instead are hatched and live their early years as grubs. Because of this, Karkat has neither nipples nor bellybutton present on his torso.-There are two faint lumps on his sides where his extra set of larvae legs had fused with his body after he pupated, and these lumps are a darker shade of gray (almost black) in comparison to his gray skin.-His claws and teeth are pretty sharp and are more than capable of puncturing human skin.-Troll skin is a bit rougher than human’s, and tougher.-Trolls that are lower on the hemospectrum (Such as rustbloods, brownbloods, and mustardbloods) generally have a higher body temperature, while those higher up on the hemospectrum (bluebloods, indigobloods, purplebloods) generally have their body temperature a little cooler. As a result, while trolls will feel warmer than humans, highbloods will still feel cooler than their lowblood counterparts.-Karkat has traits from both the highbloods and the lowbloods due to his mutant blood; despite his skin feeling warm like a lowblood, he has a notoriously bad time keeping warm like a highblood.-A troll's bodily fluids matches their blood colour; tears, sweat, urine, and other fluids will appear as the same colour as their blood, though will appear more diluted. Karkat's tears, for example, are a clear pinkish-red as opposed to clear like a human.-When trolls are grubs, their horns serve them the same way an insect's antennae serve them; they help them get a feel of their surroundings and help them navigate in the Brooding Caverns. The outer layer of the horns are soft and almost spongy, and as such a grub's horns are extremely sensitive to outside stimulation.-After a troll pupates, their horns harden and become more bone-like. They lose much of their sensitivity after pupating, and can be useful as a secondary weapon in battle.-Karkat is one of the shortest trolls, taller only than Nepeta and Tavros. He is more lean than muscular, but he's pretty strong because he spends a lot of his time training.-While Karkat's combat skills have been practiced day in and day out while he was living on Alternia and were honed during his time playing SGRUB, he's still self-taught. If someone with more complex and professional training challenged him, he'd have trouble keeping up.-When he's sleeping or he's deeply relaxed, sometimes he'll begin purring.-Karkat has a massive liking for sweets, though he'll vehemently deny it. He always keeps a small stash of sweets buried away in his respiteblock.-While an avid movie lover, Karkat can't stand horror movies. If forced to watch one it won't be long before he's huddled beneath a blanket or clinging desperately to someone or something. But he'll sit through it to save his pride, even if it means not sleeping that night to avoid nightmares.-Karkat will also sob like a baby during sad movies.-Because he's always focusing on something, Karkat is easily startled. If someone sneaks up on him and scares him he will flip his shit.-All that time spent on the computer and struggling not to sleep for fear of Horrorterror nightmares has made Karkat a bit of an insomniac; There are times when, even if he wants to sleep, he can't because he's just too used to staying awake. The times when he does fall asleep are usually when his body is too tired to give a fuck anymore, which means he sometimes falls asleep on a random pile or draped over his husktop.-Karkat is a serious cuddler in his sleep. He'll cuddle against almost anything, though he'll deny it furiously when he wakes up.-Karkat has some decent cooking skills. Though, he's more the type to make simpler dishes or throw everything into a pot and call it a stew.-He's a gamer and used to play a lot with Sollux. He won't be able to turn down a challenge, though he's prone to throwing a tantrum whenever he loses.-Karkat is a total lightweight when it comes to alcohol. It might take a little while for Karkat to get buzzed, but when he's hammered he is. When he's drunk he undergoes an abrupt change in his demeanor; he can be giddy, clingy as fuck, more cocky, and much more open about giving a shit than he is sober. He's also still a bit moody when he's drunk, shifting from giddy to grumpy to depressed to ecstatic at the drop of a hat. He's much more open to having a conversation when he's drunk and won't be so ornery, and it won't take much prodding to get him to spill his guts out for anyone who asks him. Also he's terrible with dealing with hangovers.-Despite whatever protests he might make about how stupid they are or how useless something is, he will never throw away a gift that's given to him.-He's got a soft spot for animals, and will give them the best care even if they're ornery and crabby as shit around him. Even with his Lusus Karkat made sure he was well-fed, washed, had a comfy sleeping area, and was in prime condition.-Since his hive is far away from the sea and away from violent seadwellers, he doesn't really know how to swim very well.