A/N: More detail of all the things referenced in here on my tumblr. This is a giant crossover of really random things. (Frozen, Firefly, various Kpop groups) My friends and I were just joking around, but then we accidentally created this scenario and I really wanted to write it.
Backstory for those not familiar with the crossover things: they're on a spaceship on the run from the government which did awful experiments on Elsa. Xiumin also has ice powers and comes from a planet of people with superpowers.

"…you should see Wash's dinosaur collection. He's got, like, every dinosaur in existence. Toto really liked the Stegosaurus, he kept trying to wind the spikey thing on its head like a gear…"

Elsa's clearly not listening, though, and Anna trails off. She sits next to her sister, who is perched on a step, elbows on her knees, head in her hands. "…Elsa? What's wrong?"

Elsa rakes her fingers through her hair. She doesn't bother denying or trying to hide it from her sister. Her hands drop and she wrings them.

"Do you want to stay here forever, Anna?"

Anna gapes at her. Elsa winces at her own bluntness. She wasn't going to lie about what Xiumin told her, but she could at least try to be tactful.

"That's, um, sudden. What happened?"

"Do you?" Elsa repeats, sitting up to look at Anna, because she doesn't know— how to say— Her arms wrap around her tightly as she turns away again.

Anna's brow furrows as she thinks about it. "Well. No? I want to be able to live on solid ground again someday. Run around. Roll in the grass. Pick out shapes in clouds, you know, the whole living-on-earth nine yards.

Elsa nods, like she's already thought out what Anna would say. Which, honestly, she probably had, and Anna's confirmation is not helping her nerves. Anna can see it in her eyes, in the way her breath catches and quickens, in the way she holds herself like she might fall apart. Anna continues—

"But, I mean, I would stay here. If you wanted to. We're safe. We're happy."

Right? She wonders, watching her sister close in on herself. Elsa hunches over again, and she's starting to rock back and forth. Anna wraps her arms around her sister's shoulders. Elsa shivers at the sudden contact, but her breathing starts to even out.

"Elsa. Talk to me," Anna orders gently. "What's this about?"

"Xiumin—" she starts, telling herself calm, calm, everything's okay—"He said everyone has—is like me—on his planet. That we could live there."

"Do you want to leave?" Anna asks. She feels Elsa tighten.

"I want us to be safe. All of us. You, me, the ship, everyone."

"But do you want to leave?" And Elsa can almost laugh, at her sister throwing the question right back at her, at how similar they can be sometimes.

Clanking footsteps on the metal walkway interrupt them before Elsa can answer.

"Ah— sorry— am I interrupting?"

Elsa feels sudden dread at Xiumin's voice. No, they needed more time—

"No," Anna says quickly, standing. One hand stays on her sister's shoulder. "Perfect timing."

He nods, looking out of place. "I'm sorry to pressure you, Elsa, but… I need to know."

"Yes. Of course." She forces herself to stand as well. There are questions she should ask—she grasps for them, as much to buy time as to get actual answers. "If we go with you, where will we live? How will we support ourselves?" A sudden, glaring problem comes to mind. "We don't speak Chinese—"

"I'm sorry," he interrupts. "'We'?"

Elsa blinks. Anna's hand tightens on her arm. Elsa nods to her sister. "Yes. Both of us."

Xiumin shakes his head. "I think we have misunderstood each other. You are more than welcome on my planet, Elsa. But your sister has no powers. She would not even be allowed in. I can give you, and only you, safe harbor."

There's a long silence. Anna bites her lip, not daring to look at her sister. She knows what the government did, what they would do if they ever caught Elsa again, and she can't bear that, even more than the thought of never seeing her sister again. "Elsa." She's going to tell her to go. Really, she is. She ignores the crack in her voice. "You should—"

"No."

Elsa's smiling, full and bright. Her back is straight. Her head is high. Anna remembers this Elsa, from before spaceships, before government experiments.

"Thank you for the offer, truly," Elsa continues. "It is a greater kindness than we have been shown in most of the 'verse. But I'm not going anywhere without my sister."

Anna feels a rush of relief, but still protests weakly. "But— you could be safe—"

Elsa just looks at her. There's a light in her eyes that's been gone for years. She's happy. Really and truly, at the thought of staying on the Serenity, with her sister, calm and confident and happy. Anna pulls her sister in for a hug.

"Don't scare me like that," she whispers.

"Do you really think I'd leave without you?"

"…no," Anna sniffles. "Even though you should. Be safe from the government."

"You wouldn't last five minutes without me here. You'd set the place on fire or something."

"It would take more than five minutes! I'd last, like, a whole week! Okay, maybe a couple days. Okay, fine, a day. At least a day."

"You'd steal Inara's shuttle and come after me."

"No! …I'd bring her along, duh."

Elsa smiles. The worry, the fear is gone, and it's like they're kids again. "So we should save ourselves the trouble and stick together."

"Sounds good to me."

A/N: Elsa and Anna are Simon and River, but neither is specifically Simon or specifically River. They're each a little of both of them. We'll work out which one of them is in love with Kaylee later. (Probably Elsa.) I mean, I probably won't keep writing this. But if I did, Elsa/Kaylee, yo.