I hope that in any AU where the Cullens are some different kind of supernatural creature, Carlisle is STILL a doctor. No matter how nonsensical it gets (I mean, vampire doctor is already pretty nonsensical which is why I love it so much).
Mermaids? Merman doctor.
Werewolves? Werewolf doctor.
Ghosts? Ghost doctor.
Aliens? Alien doctor.
Fae? Fae doctor.
Centaurs? Centaur doctor.
And by 'doctor' I mean, a doctor who treats humans, not whatever species the Cullens are. Centaur doctor in the OR with hospital booties on each hoof. Werewolf doctor who can't schedule appointments on the full moon. Ghost doctor who the nurses complain about because he can't do anything himself because he literally cannot manipulate material objects because he's incorporeal.
I love to think that there are great, exaggerated family legends about Uncle Emmett in the McCarty family. That they're like oh yeah he went out hunting one day and never came back, but his brothers went looking for him and found some ripped clothing next to the carcass of the biggest bear they'd ever seen. A monster. He fought that thing to the death! The bear might have gotten him, but the bear died too. It was a draw, so it means he never lost a fight. He was badass. And 7ft tall. Built of solid muscle. All the girls loved him. He was your great-grandma's favorite. etc, etc.
One year Rosalie and Emmett show up at a McCarty family reunion. There are so many cousins and aunts and uncles no one really questions it, and they're listening to these stories and Emmett's just loving every second of it; they remember him and he's become this family legend, a tall tale, their very own Paul Bunyan or whatever
Meanwhile Rosalie is muttering in the back, "I'm happy for Emmett and all, but I killed that bear."
Sam is the only 'disappearance' we get on the shifter side, really, but man that one is so sad and compelling too. And we get a little taste of what people thought!
Poor Sam phased and is out there in the woods too freaked out to calm down and take human form for two weeks. The guide says that he thought he had gone insane and was suffering from delusions. But even if he eventually realized it was all real, how do you cope with suddenly finding yourself in the body of a giant wolf? He probably thought he was going to be stuck like that forever, that his mother and Leah must be so worried about him. There is no one else to help him.
Then he comes back and can't explain where he was, is terrified it will happen again, doesn't understand what happened . . . until he shakes hands with Old Quil and he recognizes the elevated body temperature. He is summoned to a council meeting. Old Quil, Harry, and Billy explain, but having never been wolves themselves, there are a lot of gaps in their knowledge.
Having an explanation helps, but it's still scary and lonely, and now there's the added layer of knowing you're supposed to protect your people from vampires, and oh, by the way, the new doctor the next town over and his family are vampires. And this wouldn't have happened if they hadn't shown up in the first place.
And then there's Leah, worried out of her mind for two weeks, then relieved when he comes back, but then frustrated and upset he won't (can't!) tell her what happened, why he's hanging with the elders all the time, why her dad won't tell her what's going on either . . . oh well at least Emily is coming for a visit; Leah will feel better after spending some time with Emily.