"So, uh, what are you, exactly?"
"What do you mean?"
You shuffle about, your feet sinking into the warm white fur that was the infinite ground.
"Like, are you technically my mum now? Big sister? Something else?"
"Oh, I get it! I'm your big sister, now. Well, big big big big big sister. With a few dozen more big's."
Sitting down on your new big sister's fur, you eye the equipment that you had been left that would allow you to live on her. A boxy, generator-like oxygen scrubber was ensuring that you could breathe, and helping to maintain the atmosphere your new sister had recently acquired. A stove-like matter creator would allow you any meals you needed, breaking the laws of physics in the process - though breaking them no more than your new sister did. A wardrobe and a set of draws contained all the clothes you would need, and a small, strange cube, about three by three by three feet, and with a square hatch on one side, would allow you to clean any clothes you inserted into it. A large cube, about twice your height, contained a matter creation system - as well as a mirror, sink, and shower.
And last, but not least, a sleeping bag. With all of the things you had been left, you would be able to live on your new sister's body for a long time indeed.
"So, you comfy down there?"
"Yeah. Your fur's pretty soft. And you're pretty warm."
"Aaw, thank you! So, teeny tiny bro, wanna see the rest of me?"
"I guess so, Lexi."
The furred surface you are sitting on rapidly zooms backwards, reorienting itself. Before you is an utterly gigantic anthro white mare - your new big sister, so big that your home universe could easily fit in the nostrils of her horse muzzle. She flashes you a kind smile and waves, and you wave back, a bit dumbfounded.
"So, little bro, there's probably a lot of questions you wanna ask - and there's a lot of questions I wanna ask you! So make sure you're extra comfy, 'cause we're gonna be here for a while!"