write smut, of course!
Let me assure you that this is most certainly not what happens when I come back from my 8 am class and crawl back into bed, although if I shared a dorm with Remus and Sirius, god knows I'd try...
Climbing Black Into Bed
Sirius threw himself against the dormitory door rather than pushed it open, and dropped his schoolbag on the floor as soon as he crossed the threshold, heedless of the parchments that spilled out of it.
He stripped off his school robes as he crossed the floor, revealing that he had gone to his first class of the day clad only in pajama pants underneath the robes, and the robes were also dropped unceremoniously on the floor in a heap. Shoes were kicked off as well, and then Sirius was climbing into a bed with a grateful sigh.
"The best part about this pre-dawn Astronomy crap," Sirius announced, "is that immediately afterwards I can crawl back into my soft, warm bed and sleep the whole thing off."
"Perhaps you ought to actually reach your bed then," a sleepy Remus Lupin grumbled. "It's several yards further past this one, which happens to be mine."
"Mmm," Sirius snuggled in closer to the werewolf's back and slid an arm around his waist, "second best thing then."
Remus grumbled something else that was made unintelligible by the fact that he'd buried his face in his pillow. The grumble turned into a gasp when Sirius slid fingers into the gap between Remus' pajama pants and shirt.
"Wanker, your hands are freezing!" Remus twisted in Sirius' arms to shove him away, but Sirius tightened his grip and pulled Remus closer, kissing him firmly. After some token resistance, Remus kissed him back, reaching up to twist his fingers in the tangles of Sirius' uncombed hair. Sirius brushed Remus' upper with his tongue, coaxing it out of his way and apparently unconcerned that Remus obviously had not brushed his teeth yet, not that Sirius had any right to expect any such thing at 6 am.
Sirius pulled back and murmured "Third best thing." Giving an exasperated snort, Remus really did shove him back a bit this time.
"Do you think you might stop rating my performance?" he demanded.
"It's not like I'm not giving you high marks," Sirius replied before kissing Remus silent again, rolling onto his back and tugging Remus over to sprawl across his chest. Remus sighed against Sirius' mouth as Sirius arched a little, just enough to prove that some parts of Remus were more awake than others. Remus trailed a slow path of kisses down Sirius' jaw to his ear, sliding half off Sirius and pressing against his side, stroking fingertips over Sirius' chest.
"It's rather unfair of you to come over here and wake me up every time you have that sodding 5 am session," he whispered. Sirius drew in a breath to interrupt, but Remus bit down gently on Sirius' earlobe, turning the words into a soft whimper. "It would really serve you right if I pushed you out of my bed right now and made you go back to your own. I should send you all the way over there," Remus slid the hand further down to caress Sirius' hardening length, "to your cold lonely bed, completely turned on, you're already hard…"
"You would never," Sirius breathed, pushing into Remus' hand, "you want it just as much as I do." Sirius pressed the back of his hand into Remus' erection and Remus growled a little in the back of his throat.
"I'd do it, just to make you squirm," Remus informed him, still breathing in Sirius' ear and making him shiver. "You'd be all the way over there, too far away to touch me," Remus slipped a casual finger underneath Sirius' waistband, "but close enough to hear when I started touching myself…"
Sirius turned his head to kiss Remus, but Remus pulled back and refused to let him, taking his hand away from Sirius' erection.
"Lay still or I really will kick you off onto the floor," Remus threatened, and Sirius felt the heat and the command in Remus' voice go straight to his cock. "I mean it, Sirius."
Sirius settled his head back onto the pillows and watched Remus expectantly. After a moment of making sure Sirius was obeying and not plotting, Remus lowered his lips back to Sirius' ear, but instead of teasing Sirius more, he slid his hand underneath Sirius' waistband without hesitation. He grasped Sirius' cock, its hot pulse against his palm making him want to grind his own erection into Sirius' thigh, and started leisurely stroking Sirius while he continued his whispered monologue.
"I'd make sure you heard every sound," he breathed, "I might even use Sonorus so you'd have to hear every rustle, every shift, every brush of my hand on my cock. I'd push my trousers down slowly, so slowly you could probably hear the exact moment when my cock pulled free, you'd hear me gasp as the cold air hit it, chilled the smear of precome at the tip, and you'd know exactly what it tasted like…"
Sirius took a ragged breath and pressed harder into Remus' hand, begging silently for him to stroke faster. Remus ignored him, but pressed closer and closed his eyes as he sank deeper into the fantasy.
"I'd start slowly, so you'd have to listen for as long as possible, you'd hear me licking my palm, the salt on my palm making my tongue tingle, and you'd imagine me using my tongue on you, you'd know what my tongue felt like on your own hand and against your skin, warm and wet…"
Sirius made a rough noise in his throat and Remus' eyes opened a little, enough to see that Sirius' own eyes were squeezed shut and he was clenching his hands to keep from wrapping his hands around Remus' and forcing him to speed up. Remus stroked harder at the sight, and kept on murmuring in Sirius' ear.
"Then I'd wrap my fingers around my cock and squeeze, and you'd hear my dragging my fist down my swollen skin, and you'd know what every inch of my cock felt like under your fingers, under your tongue, you'd taste me just thinking about it, you'd close your eyes so you could pretend it was you stroking me, pretend it was your tongue instead of my thumb pressing into the dent on the underside that makes me cry out your name every time…"
Sirius arched up a final time, pushed beyond any human being's limit, and came in Remus' hand, gasping a wordless noise of pleasure. When he finally caught his breath enough to open his eyes, he found Remus licking his palm clean, eyes bright and chest heaving. When he caught Sirius' gaze, something snapped in Sirius' chest and he threw himself onto Remus, pushing the werewolf onto his back. Sirius bent his head to suck the spot where Remus' neck met his shoulder as now-warm fingers undid Remus' buttons and pushed the pajama shirt out of the way to stroke pale skin, every ridge of scar tissue over which his fingertips slid making them tingle.
Remus growled Sirius' name and Sirius reached down further to shove Remus' pajama pants down out of the way. Without hesitating, Sirius slid down in one smooth motion and found Remus' cock with his lips, sighing with heat as the salt of Remus' skin burned his tongue.
Sirius slid arms underneath Remus and pressed his fingers into the top of Remus' arse and the small of Remus' back, urging him to raise his hips and thrust deeper into Sirius' mouth. Sirius distantly felt hands pulling at his hair, rubbing his scalp, but his focus was narrowed to the way Sirius could taste the vein on the underside of Remus' shaft beating against his tongue. He felt the tightening of that vein first in the second before Remus spilled over his tongue and salt cauterized the back of his throat.
Sirius stayed where he was for a minute or two, running his tongue and lips over Remus leisurely until Remus' hands fell to his shoulders and urged him up. Sirius pulled himself up to lay his head on Remus' chest, Remus' heart thudding in his ear, still pounding but slowing as Remus relaxed back towards sleep.
"Fourth best thing," Sirius yawned, and Remus thumped him hard with a fist between the shoulder blades.
At breakfast several hours later, a freshly showered Sirius plopped down next to Remus with a yawn.
"I think I'm starting to warm up to this 5 am Astronomy business," Sirius said casually, reaching over to brush Remus' thigh under the table.
"We KNOW!" James and Peter snapped in unison.