A/N: I saw this prompt on Tumblr, and thought it sounded fun so… here we are. It's set pretty much any time after Tick, Tick, Tick and Boom! in season 2. I hope you guys enjoy it. Let me know what you think!

After knocking loudly, he rocked on the balls of his feet, hands thrust deep into his trouser pockets while he waited patiently for her to open the door. Open the door she did, but pay him attention she did not.

"Beckett?" he asks, stunned by her appearance. When she'd called him up and asked if he'd be interested in joining her for some Chinese takeaway since there'd been some kind of mistake with her order, explaining that she'd somehow managed to end up with a meal for two, he'd leapt at the chance to spend some more time with the woman who was steadily becoming his best friend. It wasn't often they managed to do things outside of work. After a full day, working either a case or filing paperwork, Kate Beckett always preferred to just head home and sink into a relaxing bath. Not that he would begrudge her that. Perhaps if he contributed more to paperwork, she'd repay him with a burger and shake at Remy's. But that would mean giving up playing around with the stuff on top of her desk and just generally annoying her by not helping. Aggravated Beckett was almost better than smiley, soft-talking Beckett.

"What, Castle?" Kate demanded, returning to the door in exasperation. Exasperation because instead of just walking into her new apartment and shutting the door behind him like she'd expected him to, he was still standing out in the hallway, staring at her.

"Is- Is that my shirt?"

He'd been wondering exactly what fate had befallen his red shirt ever since she'd bought her new apartment. With the damage from Dunn's bomb, her old place was hardly habitable. Threat hanging over her, he'd of course welcomed her into his home with open arms and assured her she could stay as long as she wanted. But in the middle of the night, they'd hardly been able to go and buy her any replacement clothes. All she had was the spare clothes she kept in a locker at the precinct. Lending her a pair of joggers she could tie around her slim waist and a baggy t-shirt was no trouble at the time, and he didn't even notice their disappearance until long after she'd moved out. If he hadn't decided that his fitness level was low enough that he could no longer keep up with Beckett and the boys while chasing a suspect, he probably would never have discovered that his shirt was missing.

As it was, he just assumed he must have mislaid it. Certainly the last time he remembered seeing it had been when it was covering up his favourite detective's body before and after bed the first night she stayed with them, but he would never have guessed she would steal his clothes. He was sure she must have already washed and returned it.

Glancing down, Beckett flushed. "Right, sorry, it is. I completely forgot about returning it to you after I moved out."

"It's no trouble," he replied, the polite response ingrained into him after so many reprimands from his mother when he was an unruly child running around the theatre and barging into people's dressing rooms. He smiled, finally stepping into her apartment and shutting the door behind him before watching her busy herself in the kitchen, pulling cardboard containers out of a paper bag and opening them up to dish up their contents onto two plates. Although it was just takeout, it still reminded him of the morning he'd woken up to find she'd cooked him breakfast.

"You remember where the cutlery is, Castle?" she asked, startling him out of the happy memory.

He nodded, rushing into the kitchen to grab two forks from one of the drawers while she carried the two plates to the table. While he sat down, she wandered back into the kitchen, her bare feet pattering against the floor tiles while she reached into a cupboard for wine glasses before offering him the choice of red or white.

"Whatever you're having," he replied diplomatically, leaving his cutlery sat beside his plate and his food untouched, waiting for her before he began eating.

"Here," she said, setting a glass of red Bordeaux on the coaster beside his plate. As soon as she had taken her own seat, she took a sip of wine and smiled at him. "Thanks for joining me, Castle. There's no way I could have eaten all of this by myself."

"Good food, good company; I can't complain." A moment of silence reigned before he spoke again. "The apartment's looking good." The last time he'd been there was to help her shift the few things that had been salvaged from her apartment and the number of things she'd been able to pick up since – mostly though just new clothes and new copies of his books.

She nodded. "I've just about got everything unpacked. Thanks for helping me move though, and for you know letting me stay with you."

"It was no trouble. You're always welcome at casa de Castle. I know for a fact, Mother has been missing your cooking ever since you left."

Rolling her eyes, Kate just took another bite of her Peking duck; sure he was just exaggerating on her behalf. Unbeknownst to her, he saw the little rolls of her eyes as well as the small, satisfied smile splitting her lips. He couldn't stop looking at her in his shirt. Before, well, before she'd only been wearing it as a substitute for a pyjama top. But now, she'd obviously chosen to wear his shirt. And for some reason that sent a little flare of happiness through him.

He finished his wine of the sofa, staying after the meal to let his food digest while she flipped between channels on the TV, trying to find something to watch.

"Ooh, they're showing reruns of Buffy!"

"We are not watching Buffy the Vampire Slayer, Castle." After going through practically every channel and not finding anything much better though, she was forced to concede and flick back. "I should probably go and change so I can give you your shirt back-"

"-S'fine," he mumbled, clearly focusing more on her television screen and Sarah Michele Gellar's lack of clothing than what she was saying.

Walking to the door with her though an hour later, pulling his jacket on, he surprised her. "I meant it by the way. You can keep the t-shirt."

Unable to formulate a proper reply, stuttering over words that didn't make any sense when put side by side; Kate looked at him, wondering why exactly he wanted her to keep his shirt. They were friends. Sharing clothes – or rather giving or stealing them… well, it was a couple-y thing to do. It made her feel uncomfortable, even when she knew she'd been hanging on to his shirt in the first place because it smelt like coffee and wood, two comforting smells that she'd come to associate with Castle. Smells that made her think about the few weeks she'd spent living with him and his daughter and his mother, bringing a smile to her face even at the end of a long day.

By the time she'd managed to work her way into a thank you, she looked up to find her door already open and Richard Castle disappearing down the hallway, whistling cheerfully to himself.

A/N: Pretty short, I know, but I wanted a chance to kind of write some Castle/Beckett friendship stuff, something light-hearted after the finale. Let me know what you think? Like I said in the description, I could be persuaded to extend this in a series of related oneshots about the shirt. I've got a few ideas floating around. So let me know if you're interested in that.