A/N: It's currently 2:22am, and I have to be up early for class tomorrow, but I just had to get this done. This idea came about after reading one of those tumblr Castle confessions. It got the wheels turning, and after the last story I posted, I felt the need to write some serious fluff. Hope you all enjoy it and happy early Christmas!

Disclaimer: All I want for Christmas is Castle. I would not be saying this if I already owned it.

He insisted on having a Christmas party at the precinct.

It took forever to get Gates to agree, but after swearing that he would put up the decorations that morning and take them down that night all by himself ("No recruiting my detectives into helping you decorate, Mr. Castle!" she had said, shooting a glance at Ryan. "They have better things to do with their time!"), the hardheaded captain had finally granted her permission.

The entire week, he was practically shaking in excitement and anticipation, and Kate spent most of their time together rolling her eyes at him. They had been an official couple for over a year and a half now, and yet she still wasn't completely used to his childish antics. She wasn't sure she ever would be.

In the few days before the party, he spent less and less time at the precinct. She would show up at the loft after work to find boxes upon boxes of Christmas decorations stacked in the living room.

"For Tuesday," he said, grinning from ear to ear. "This is going to be a Christmas Eve party the likes of which no one at the Twelfth has ever seen."

And, boy, was he right. She could hardly believe her eyes when, as she and her team steadily worked a case Christmas Eve morning, he slowly turned the precinct into what looked like a tiny North Pole. Garlands tied with red bows lined the walls, nutcracker statues stood sentry at the entrances to the bullpen, an eight-foot-tall Christmas tree – elaborately decorated – sat glistening in the corner. She even noticed a few sprigs of mistletoe hidden here and there (she caught Ryan and Esposito awkwardly dodging them a few times).

And when she saw the conference room (fake snow expertly placed on the floor, big plastic candy canes lining the walls, a beautiful gingerbread house sitting on the table), her jaw literally dropped. She knew that Castle had a thing for extravagance, but this – all of this – was an entirely new level. Something had made him decide to really go all out this year.

He must have set up a subtle speaker system because when shift ended at five, Christmas music promptly began to play in the bullpen, loud enough to be heard but soft enough that no one would object to it. Sitting at her desk, she turned around to seek him out, overwhelmed by everything he had done, but Castle was nowhere to be found.

"Wow," Ryan said, materializing next to her desk and looking around in wonder. "Castle did all this?"

"Seems like it," she said, a small smile gracing her features in pride. "Speaking of which, have you seen him?"

Ryan shook his head. "Not recently. I saw him leave about an hour ago, but I haven't seen him si-" He cut off as his eyes flicked to the elevator and his jaw dropped.

She turned to see what he was looking at and was also stunned into silence.

Castle was stepping off of the elevator with four other people carrying trays, a huge grin on his face.

He was dressed in a complete Santa costume, beard and all.

She watched in awe as he strode into the bullpen, directing the caterers into the conference room where they began to lay out the food before he turned to her and Ryan, still shell-shocked at her desk.

"Do you like it?" he asked, voice saturated with giddiness and only slightly muffled by the beard.

Ryan worked his jaw, trying and failing to speak a few times, before he said, "I . . . I gotta go find Javi."

Once he had run off, Castle turned his bright blue eyes to Kate. "What do you think?"

She smiled at him. "It's spectacular, Castle."

His eyes crinkled at the edges. "Yeah?"

"Yeah."

He took her hand and pulled her towards the conference room as the caterers began to clear out. "Does everyone know to come up here for dinner?"

She nodded. "I had Ryan and Esposito spread the word around."

"I thought the team wasn't allowed to help with this," he said, brow furrowing.

Beckett shrugged. "Gates said that you weren't allowed to recruit help. She said nothing about me."

The smile she gave him then cracked his heart wide open. He pressed a kiss to the back of her hand. "Thank you."

She opened her mouth to say something but was interrupted when Ryan made a sudden reappearance with Esposito and Lanie trailing behind him.

"Ay yo, Castle, you did all this?" Esposito asked.

Castle nodded. "Sure did."

"Nice, bro." He gave him a fist bump before saying, "Let's eat. I'm starving."

He and the others began filing in, taking seats around the long table and grabbing plates, but Castle turned towards Kate, hope shining in his eyes that she would finish what she was going to say. She just gave him a small smile, however, and tugged on his hand, leading him to take a seat with the others.

For the next few hours, people flitted in and out of the conference room to share in the Christmas Eve dinner. LT made an appearance with his young daughter, Ann Hastings (recently promoted to detective) showed up with her soon-to-be husband Paul, and even Gates stopped in to sit with them for a while, her features softening in the glow of the Christmas lights strung up on the walls.

The evening passed in a swirl of color and laughter. Beckett sat as close as she could to Castle (who lost the beard once it came time to eat), their hips pressed against each other. His hand kept creeping down to run over her thigh and she occasionally tangled their fingers together. Lanie kept trading looks with her, the former raising her eyebrows while the latter just shrugged, too happy to do much else. Kate even caught Gates eyeing them a few times, but their stern captain must have been subdued enough by the Christmas spirit to not say anything.

By eight o'clock, only the six of them remained. They continued to talk for a little while, discussing Ryan's newborn baby boy, when the proud father stood up and began putting on his jacket.

"Speaking of which," he said, "I really should be getting home. It is his first Christmas after all, and I don't want Jenny waiting up too late for me on Christmas Eve."

Castle stood up in a flash. "Before you do, if everyone could just move out to the tree really quick." He noticed the look Gates was giving him. "Yes, even you, Captain."

He shepherded them out into the bullpen and in front of the tree. Kneeling down, he reached underneath the beautiful evergreen and began to pull out presents, handing them out to their respective recipients.

There was a flurry of movement as wrapping paper and tape were torn apart and thrown aside. Lanie was the first to get to her gift, exclaiming, "A spa certificate?!" She fixed her eyes on him, intense. "Richard Castle, are you sure you're not single?"

His only response was to hook his pinky with Kate's and tug her closer to him so he could wrap an arm around her waist.

"Bro, this is awesome!" Esposito had unwrapped the new Madden. "Madden tournament on Saturday?"

"Yeah, sure," Castle said with a smile. "Ryan, you in?"

But Ryan wasn't paying attention. "Aw, Castle, this is cute!" He was holding up a small argyle sweater vest with matching slacks, dress shirt, and clip-on tie.

"So, Patrick can match his dad," Castle told him.

Ryan moved to give him a one-armed hug, made difficult due to the fact that Castle wouldn't let Kate give them any room, keeping her firmly pressed to his side.

"Thanks, man," Ryan said once he managed to untangle himself. "But now I really do need to be going-" Five heads turned as Gates let out a shriek.

"My two missing Gemini collectibles!" She pressed them to her chest protectively. "Thank you, Mr. Castle. Thank you." Then she took off for her office, probably to put the dolls away before any harm could befall them. Again.

"Nothing for me?" Beckett asked, half-teasing.

"Later," Castle said, pressing a kiss to her temple. "When we get home."

Ryan clamped his hands over his ears. "LA LA LA! Not listening! Bye, guys! Merry Christmas!" he said as he darted away.

The others called out Merry Christmases back (barely restraining their laughter), except for Castle who shouted "That's not what I meant!" But Ryan was already gone.

"I think I'm going to follow his example and head home as well," Lanie said, tugging on her coat.

Esposito also made a grab for his jacket. "Me too. I'll walk you out."

As they got ready to leave, Kate finally managed to extract herself from her boyfriend's grip. "I think we should go home too, Castle."

He sighed. "I still have to clean all this up, remember? I promised Gates."

Kate shot a look over her shoulder. The captain was talking to someone on the phone, still starting at the Gemini dolls and beaming. "Oh, I don't think she'll mind. Besides, I want to give you your gift." She leaned in close and murmured. "And yes, I did mean it like that."

Esposito shot her a disgusted look. "Yo, get a room."

"We're trying," she said with a smirk. "You're slowing us down."

"Wow, nice job, Esposito," Castle said. "I can never slow her down. It's usually just-"

"Okay, I'm moving, I'm moving!" Esposito hollered, half-running to the elevator.

The loft was quiet when they got back, with only the glow from the gargantuan Christmas tree in the middle of the living room there to greet them. Alexis and Martha were at their own respective Christmas Eve parties and had promised to be back late.

"I still can't believe you dressed up in a full Santa costume," Kate said as he helped her take off her jacket.

"Really? With everything else I've done in the past, you still can't believe I'd do something like this?" He gestured to the red suit.

"Well, no," she said. "I can, I guess. It was just surprising." When he had finished hanging up her coat and turned back towards her, she stepped in close and pressed her hands to his chest. "You still surprise me sometimes, Castle."

He wrapped his arms around her and pressed a soft kiss to her lips. "And you still surprise me, Kate. Every day." He kissed her again. "And also, this suit does have some pretty great advantages."

Kate raised an eyebrow at him. "Like what?"

He smiled, took her hand and tugged her towards the couch. Sitting down, he pulled her onto his lap. "Tell me, Kate. What do you want for Christmas?"

She barked out a laugh. "Are you serious?"

His blue-eyed gaze didn't waver. "Yes."

"Okay then, Castle." She shifted until their mouths were barely an inch apart. "All I want for Christmas-" She kissed him. "-is you."

Castle pulled away, pouting. "No quoting cheesy Christmas songs," he protested.

"Why not? It's true."

"I can't give you something you already have, Kate."

She sighed. "Castle, everything I need is right here." She cupped his jaw with her hand and ran her thumb across his cheekbone. "Just you."

"Fine," he said. "Then I guess I don't have to give you your present."

That same hand moved to twist his ear. "Don't you dare."

"Ah! Okay! Apples!"

She released him, smiling softly. "Castle, I'm sure whatever you got me is fine. Why are you even asking me this?"

His wide grin almost completely disappeared in an instant. "Because it's not about what I got you. It's about what I'm willing to give."

Kate's brow furrowed. "And what's that?"

Castle regarded her for a moment before reaching into his jacket pocket and pulling out a small velvet box. "A future," he said. "With me."

She gaped at him. "Castle-"

"Kate." He opened the box to reveal a simple yet gorgeous diamond ring. "Will you marry me?"

She stared for a long while at the ring before looking up at him. "Castle," she said slowly. "Rick . . . You want me to be . . . your wife?"

He shook his head."No, Kate," he said. "I want you to be my everything."

There was another long moment of her looking back and forth between him and the ring before she said, "Castle, I will only marry you on one condition."

He took a deep breath. Let it out. "Yeah?"

She smirked and turned herself so that her knees were braced on either side of his hips. Looking him dead in the eyes, she said, "I am not dressing up as Mrs. Claus."

He burst out laughing. "You drive a hard bargain, but I'll take that deal."

Both of them still giggling, Castle pulled the ring from its box and slipped it onto her finger. Kate only regarded it for a moment before swiftly leaning in to press her lips to his, hard. The kiss quickly began to escalate, and when they broke apart for air, Castle gasped, "Is it time for my present now?"

Kate grinned, pressing their hips together and drawing a groan from him. Her mouth at his ear, she murmured, "Tell me, Castle. What do you want for Christmas?"

A/N: So for anyone who was wondering, that tumblr confession was "In Secret Santa, I really want Castle to be wearing a Santa costume for whatever reason, and for Kate to sit on his lap and tell him her Xmas wish." So person who asked for it, this one's for you.

Like I said, all I want for Christmas is Castle. But I guess reviews are good too.