Unavoidable
[http://archiveofourown.org/works/168274/chapters/245496] - - public:opalsong
prompt runs: Bad End AU where all the trolls and kids are together on the asteroid behind the Veil. So the facility they have there has tons of weird machines and stuff. John and Karkat for some reason are exploring some parts no one's been in yet and through. Cue some tripping/curious button pressing whatever, so long as john someone gets zapped by some sort of crazy dna altering device and whoa! Suddenly troll!John. And Karkat has to help him deal with the new changes (Horn sensitivity and troll anatomy being fairly different from human anatomy) , even though it he bitches about it the ENTIRE time. There are sexy results at some point. Bonus - He ends up with a fairly high ranking blood type which reaaally pisses Karkat off.