Not my characters. Mixes Firefly, Supernatural, and Good Omens. I have enough unfinished fics that I feel guilty starting another one, but this simply won't let me go.
Firefly - Post-Serenity
Supernatural - Nothing after Season 5 is canon.
Good Omens - Crowley and Aziraphale "made the effort" and having been making that effort for centuries.
...
Mal went to the bridge to let River know it was time for dinner, and she could feel free to put Serenity on autopilot. He wasn't surprised that she turned to look at him before he said a word.
"I have a story to tell you," she said, playing with a lock of her long black hair.
"Do you now, Albatross?"
"Won't take long, we can go eat after I'm done. It's a little way of telling a big story." It was hard for her to explain about the things she knew and learned the way she shouldn't have been able to, at least in terms that made sense to others, but she was getting better at it. "Earth-That-Was nearly died many times. Many times. There were those that fought for it. Big Damn Heroes. One day it was too much. They knew Earth-That-Was would die, and they couldn't stop it. So they pushed all the folk they could to build the ships that would save them, and flew them to safety in the arms of the angels that loved them. So we never walked the Earth again. And they do not walk among us, leaving enough alone. Except..."
Zoe came up behind Mal. "Sir? Just received a wave. We have a job, and this one's even legal, if you want to go negotiate."
"Lovely story, darlin'. Best you get some food before Jayne gobbles it all." Mal headed towards his quarters.
River allowed herself a secret, slow smile. "Here come the birds," she whispered.
...
"Now I want all of you to be polite to Mr. Castiel here," Mal announced to the crew as they stood around the gangway, gawking at the new passenger. "He's paying us good money to take him to Badger."
Zoe had fallen ill, unusual for her, so she was not present to meet Castiel in the flesh when the rest of them did. The man was not very tall, but seemed solid and stern. He wore an old-fashioned black suit, a blue necktie, and a tan overcoat. Kaylee thought he would be cute if he smiled - she loved Simon but no harm in looking at a bit of shwie. Simon thought he seemed a little off in some undefinable way, like he wasn't used to being a person, which made no sense at all. Jayne wondered if the fella needed some laxatives or something.
"How long until we reach Persephone, Captain?" Castiel asked, inclining his head slightly.
"Shouldn't be more'n a week if all goes smooth. Will you be needing help with your things?"
"Beyond safe and speedy passage, I think not."
"I mean, your, um, your luggage."
Castiel tilted his head quizzically. "I have no luggage. Perhaps we should depart now."
"O..okay..." To cover his bewilderment, Mal turned to his crew and barked, "Everyone back to your posts. Doc, since you haven't got someone to attend to at the moment, show Mr. Castiel to his cabin if you would be so kind."
Simon nodded and approached the new passenger as everyone else trickled away. River gave him, and then Castiel, a huge smile and a wink before she returned to the bridge. Ai-ya, she had better not taken too much a liking to the man...Simon was hoping this stage of worry wasn't quite upon him yet...
"Doctor Simon Tam. Pleased to make your acquaintance," Castiel said, as if by rote.
"Thank you. Follow me, Mr. Castiel." Simon led him towards the sleeping quarters.
"Castiel will suffice."
"Is it your first or last name?"
"I do not understand the question."
Simon wondered if the man was teasing him, but those bright blue eyes seemed nothing but sincere. "Your family name or given name. Which is it?"
"My family..." Castiel looked distant for a moment. "My family name is 'Winchester'."
...
Kaylee knocked on Castiel's door after she'd finished inspecting and maintaining the engine. "Hey, Castiel?"
"You may open the door," Castiel replied.
She saw him sitting on the edge of his bunk, feet on the floor, hands by his sides, with his shoes and coat still on, looking at nothing in particular. "Simon and Jayne and I was going to play cards. We usually bet with chores, but you don't have to bet or nothin', I just thought you might like some fun."
"I do not wish to be a burden."
"Oh, no, not at all! It's nice to meet new people." And she beamed at him.
He stared at her for a moment like she was something both precious and puzzling. Then he stood. "I will do my best to learn the game."
...
After the first two rounds while he was still learning, Castiel won every single hand of the game. By the sixth round Jayne growled, "This ain't right. You said you'd never played before."
"And I never have. I played poker once, long ago, but not this. Are you not having fun?"
"I think you're cheating."
"Why would he cheat if he's not wagering?" Simon asked.
"And you should be nice to someone new," Kaylee added.
"You are suspicious of others, yet you are the least moral and cleanly of us here," Castiel commented.
Jayne scowled and gave him a small shove. "Fancy or not, you don't get to insult me."
That's when the little man with hands that looked like they'd never seen a day's manual labor picked Jayne up by the front of his shirt, not using any visible effort. "Please, I am not here to pick fights with the people of this ship. And you are distressing the others." He put Jayne back down. "Got it?"
Jayne gulped and nodded. "Got it."
...
Zoe and Castiel both picked at their food when mealtime came. "I don't know what's up with me today. Can't seem to keep anything down," Zoe mumbled.
"It's because you're with child," River said nonchalantly. What's worse is that Castiel said it as well, at the exact same time.
A long, awkward, shifty silence descended upon the crew. Castiel looked at everyone. "I mean to say, congratulations."
"Gorramit, Mal, you picked up another gorram Alliance experiment!" Jayne put his hand on his knife.
"Seems there's some things you didn't tell us, Mr. Castiel," Mal began.
But before he could continue or anyone else could jump in, River said, "He was at the Academy with me. They had good success but he couldn't fight so well because they found him older. Stronger, not so quick. They said he died on the table. Must have fooled them. Must have escaped. No one's after him, though. He's quite safe. Safer than me."
The other crew members seemed a bit dubious about how plausible this was, but River sobbed very convincingly at her "painful memories".
...
"Why did you lie for me?" Castiel asked, standing in the doorway of River's room.
"Because you're made of light and ice, fire and sky. Because they're not ready. Because you're not the first angel I've met."