A brief disclaimer- this one shot is part of the Disinherited AU, in which Sirius is not actually biologically part of the Black family.
"Trixy?"
"Hm?"
"Do you think my mum would be mad if she walked into the kitchen and all the dishes were stuck to the ceiling?"
Bellatrix and her idiot adopted cousin were in the Black manor's library. Bellatrix sat at a table, writing an essay for her DADA summer homework, having finished her outline yesterday. Sirius, meanwhile, had not touched a quill in over a month, and currently hung upside down from a bookshelf, legs curled over the edge, reading some Muggle superhero comic (which Bellatrix had not at all borrowed frequently and read when her parents were out). He was stupidly attractive, even completely red in the face with all the blood going to his head, and Bellatrix had to kick herself whenever she'd been staring for too long.
"Merlin's beard, Sirius. Just do your homework."
"Come over here and make me."
She rolled her eyes before getting up to poke his forehead. "Come on. Let's see you do something useful." She continued to survey him. "You should really get down from there. Your face has managed to get even redder than before."
"I'm…" he avoided her gaze. "It appears I'm stuck."
Bellatrix started laughing. "Oh, Sirius."
"Are you gonna help me, or what?"
"Okay, okay." She levitated him and tugged his arm to bring him down from the bookshelf. "You're down now. Will you do your homework?"
"Only if you help me with my prank."
She stared him down. He stared back.
"Please, Trixy? Then I'll do all the homework! I'll make outlines! I'll make flashcards! I'll—"
"You promise?"
"Promise, promise, promise."
"Alright, Sirius. Let's stick some dishes to the ceiling."
"Let's go!" Sirius punched the air. "You won't regret this."
"We'll see about that."
"Come on!" He seized her hand, and she pretended to think nothing of it. "We should start with the best china."
So they ran through the darkened corridors, which for once, didn't seem so dark, and his hand was sweaty, but it was fine, she didn't care. She could only wish that life would stay like this forever.