Dream involving some iteration of canon Karkat coming across a Terezi and Kankri from a humanstuck werecreature AU, and being really offended upon discovering that they got along and had multiple inside jokes which he didn't understand. They even had matching terrible Tumblr usernames referencing insufferably twee slash fanfic tropes for a nonexistent 90s cartoon they'd both liked.
I don't remember what my brain came up with for the usernames, but it was like Terezi was "character-a-bringing-you-soup-while-you're-sick-in-bed" and Kankri was "character-b-pretends-to-burn-his-finger-on-the-soup-and-wants-you-to-kiss-him-to-make-it-better." Karkat threw a shit-fit about this at them in a chat-log and they started co-writing fluff fic at him. Kankri was actually taking it pretty seriously and trying to pretend he wasn't, to Karkat's immense embarrassment.
Terezi was a police detective or prosecutor and, obviously, a were-dragon - I think a Dragon King With A Beautiful Daughter-type dragon rather than a Princess Stealing-type dragon, though. Kankri had some sort of more-important justice department or federal court position he wasn't very good at, and was for some reason a were-bear. He threw his harder decisions on Terezi because he was a huge coward.
This turned into a more-serious story, an Inspector Chen AU involving the three of them going to hell to search for the ghost of Karkat and Kankri's cousin, a little girl who'd run away from heaven to stay with the ghost of Evil Signless. Hell was sort of like a post-apocalyptic San Francisco airport where people were "living" in little privacy shelters they'd thrown together from bits and pieces of the equipment. Heaven was the Incheon airport.
Evil Signless, meeting Kankri for possibly the first time, was very disappointed in him, and sort of possessed him/gave him the Evil Signless Brain Virus. Kankri's personality wasn't actually over-written, and he and Terezi were kind of observing the changes in the way he was acting and going "this could actually be okay," thinking he might be less shitty at his job now. Karkat was at this point avoiding all interactions with Kankri, and didn't even notice it had happened.
Kankri was useless with the little girl even when sorta-possessed, so he went back to see the girl's mother/guardian in the world of the living. The mother was under arrest for killing someone and either embezzlement or Evil Magic, all of which she'd done. However, there were extenuating circumstances involving the murder victim (her husband?) threatening her and messing with her finances to make her dependent on him, and maybe doing something bad to her daughter's ghost. (He hadn't killed the little girl, though; she'd died years or decades earlier.)
The Evil Signless Virus was directing Kankri to coax this woman into doing/testifying to stuff that served some nefarious purpose of his, but Kankri's personality kept sort of overturning it because the habit of asking Terezi for guidance constantly was too ingrained.
I woke up just as the POV was switching back to Terezi and Karkat, still in hell and trying to convince the girl to come home. The main iteration of Evil Signless was there delaying them, trying to give whatever he'd done time to take over Kankri's brain.