Undertale AU Sibling Oneshots

Dreamswap! Nightmare x Sister! Reader

(A bit of a confusing AU, so hope I did well! It was also requested that the characters are still skeletons, which I'm happy to oblige there.)

Requested by the lovely corvid, @CameronPeterson2!~

You held back the giggle that threatened to slip through your mouth, seeing Dream walking into the room covered in black paint and silly string. Ink stared wide-eyed next to you, the pupils in his sockets currently making '?!' symbols.
You quickly swallowed your amusement before either could see your expression.
"Are you alright?"
"Just. Fine." Dream spoke through gritted teeth, heading off to the bathroom to get clean.
You waited until you heard the door click before you headed off to your room, glancing around to make sure Ink hadn't followed you before you opened a portal and jumped through, only bursting into your fit of giggles when it closed behind you.
"Enjoy that one?"
You looked up to see Nightmare, your giggling picking up at the sight of his shit-eating grin. You nodded, taking a moment to try and catch your breath.
"It was really good! I'm guessing you and Error's work?"
Nightmare nodded, leading you further into his hideout, tossing you a bag of your favorite (snack) as you passed the kitchen into the living room.
"That'll keep Dream busy for a while." Nightmare mused, looking proud of himself. "The trap is magically designed to refill and drop on him three times. So that's one down so far!"
You snorted, popping open the bag to your snack.
"Some days I wish Dream didn't keep such a close eye on me, I'd join your side in an instant!"
"Wouldn't work," Nightmare smiled at you softly, "you don't have a negative bone in your body, you just like harmless pranks."
"I know." You sighed, "Dream just gets so stuffy and suffocating!"
Nightmare's eyes lit up at your words. "Ooo stuffing. We could do something with that!"
You broke into giggles again, shaking your head. "Nightmare! That's the third prank idea this week!"
"I know, isn't it great?"