Inspired by "Switched" by This_person_cant_write on Ao3. They gave me permission to write this. Make sure to go and check out their fic!

He never remembered falling asleep, but he wakes up anyways.

The first thing he notices it that it is cold, freezing in fact, which sets of warning bells immediately. He's not supposed to be cold! He's Jack Freaking Frost! He can't be cold, he hasn't felt cold since he had woken up in his lake!
He calms himself down, forcing himself to look around and stop panicking. He's in wooden room, on a small beaten down bed. There's half melted candles on the floor, flames blown out. There's a small bowl filled with water, a ripped piece of cloth placed on the rim. Jack tries to walk towards it, hopefully to get a glimpse of his reflection, but he stumbles and nearly collapses as he steps of the bed.
Why does he feel so much heavier than usual?
He eventually manages to pick up the bowl, splashing water on himself accidentally (Why isn't the water freezing?).
The water takes a moment to settle, a moment in which he looks around the room. His staff (thank the gods, he's not completely powerless, at least he has his staff) is against the wall, and there is a door to the left of him, where another bed lay. He turns his attention back to the water bowl, and nearly screams.
There, in the distorted, half-shown reflection, he sees the face of Jackson Overland staring back at him.

Jackson wakes up in a unfamiliar, cold place.
The cold part wasn't unusual, of course. His family's house is always cold of late (it's the dead of winter, after all).
The fact that there is snow in his room is more strange. There is piles of fluffy flakes everywhere, scattered throughout the room. The walls are decorated with frost over green paint, and the floor is iced. There's not a bed, but a large cloth-like thing stretched between two of the ceiling beams. He doesn't particularly know what that is.
A wind blows through the open window. Why is the window open? Shouldn't it be closed, to keep out the cold?
Which makes him realize something. He's not cold, despite being ankle deep in snow and having no cloak on. Where did his cloak go? All his clothes are gone, though his pants look recognizable. He's wearing a weird, bright blue garment. Where did that come from, and why was he wearing it? The cloth was soft, and most likely expensive. Where did his belongings go?
He pulls himself out of the snow, scattering it all over the ice floor.
He slowly stands up and looks around. There's two doors, probably leading outside of the room, though why you would need two he couldn't understand. He goes through the closest one.
It's not a door outside. Instead, it's to a small room that he doesn't recognize, one with a weird seat and colorful curtain made that shines in a light coming from the ceiling. How did one take the sun's light and put it in a room?
He turns, taking in the room, and sees a reflective surface. More clear and colored than water, sharper and cleaner and easier to see.
Jackson screams as a white haired boy stares at him from the glass.