For Dragon_Writer993, who wanted a story about Christmas in the Underground.

As a disclaimer, the rest of the one-shots will NOT be this long. She wanted it set in the Reset-verse, and so my feels got away from me. But consider this my Christmas/Sorry-I-Murdered-Everyone-in-the-Last-Chapter present.

~

                There was something really great in being a sentry in Snowdin during Christmastime. The kids coming up to see Santa, the lights, the big tree in the middle of the square—sure, everything except Santa was there year-round, but the energy and excitement made it much more fun.

Papyrus had been taking his job even more seriously than usual, determined to protect the festivities from any and all threats. It resulted in a lot of running at non-existent enemies, then coming back to insist that obviously he had frightened off any ne'er-do-wells. Sans always agreed. After all, who was he to ruin his brother's fun? And it wasn't like he was the one running.

Christmas Eve came, and, as to be expected, Asgore gave his guards and sentries the okay to head home early. Since they were in Snowdin, Sans and Papyrus also got their tree on the house. They were carrying it back to their place in the Core while Papyrus laid out the plan for the rest of the day.

"So we'll sing carols until three, then obviously visit Santa—"

"You could've visited all week," Sans pointed out, trying to keep needles from hitting his socket. Papyrus looked over his shoulder, giving Sans a horrified look.

"I was on-duty, Sans!"

"And?"

"And that's breaking the rules! That gets you on the naughty list!" Papyrus huffed. "Honestly, if I didn't vouch for you every year, you'd never get any presents."

"You're right, Pap. I'd really be in trouble without your presents of mind. I'm really lucky that yule log all my good deeds to Santa, or I'd be without Clause to cel--"

"SANS, I WILL PUT YOU ON THE NAUGHTY LIST MYSELF."

Sans laughed as they entered Hotland, then slowed as they approached the Lab. He'd followed Gaster's instructions and hadn't contacted him since he'd told him the research was over. But...well, what did he do for Christmas? Was he just...alone?

"Hey, Pap?"

"If it's another pun, I'm not listening."

"Nah, not now. Listen, how attached are you to our usual schedule?"

Papyrus stopped walking and looked back at Sans, browbone furrowed. "Why?"

Sans winked. "I think it's about time we changed things up. Wait here, bro."

"Sans, what--?" Papyrus huffed as Sans teleported away. "Why does he always do that?"

~

The lab was quiet, as it often was now. Gaster had told Alphys to go home earlier; she'd talked about nothing but what gift she'd gotten Undyne and how she hoped she liked them, so he finally told her to just go and give it to her. (Apparently it was a replica of a very large sword. From the little he knew of the Captain of the Guard, Gaster assumed she would like it immensely.)

For himself, a quiet night in the lab was a fine way to spend Christmas Eve. He had some notes to go over regarding his and Alphys' new project—he'd have to tell Sans about it once they were sure the machine could work—and had just sat down with a mug of tea when he heard the door open. He smiled.

"Alphys, you did not need to come back," he called. His browbone furrowed as he heard a strange rustling in reply. "Alphys?"

"Well, uh, not quite."

Gaster blinked, and he quickly got to his feet as a smile spread across his skull. "Sans?" His smile widened as he saw a taller skeleton enter with a huge box of decorations. "And Papyrus! And...a tree," he added as a tree surrounded by blue light floated into the room, followed by Sans. "What on earth are you all doing here?"

"As sentries and defenders of Christmas, it was our duty to bring joy to those even outside of our patrol boundaries," Papyrus said grandly as he set the box down and grabbed a hold of the tree. He nearly fell backwards as Sans released it. Gaster held back a laugh.

"Well, you are certainly doing your duty," he said, giving Papyrus a solemn nod before walking over to help him. "Now, we could set this in the middle of the lab. Do you need help, Papyrus?"

"Of course not! I'm training to be in the Royal Guard," Papyrus said, then heaved the tree up and assured in a strained voice, "This is nothing," as he made his way to the middle of the lab.

Gaster smiled, then looked over at Sans. So why are you really here? he signed.

Sans winked. To bring happy, obviously, he signed back before picking up the box of decorations and carrying it to the tree, where Papyrus was trying to subtly catch his breath. He looked up at Gaster, then set the box down and signed, Do you want us go?

Gaster chuckled and shook his head. He looked at the tree as Papyrus got it to stand up straight. "You know, it has been a long time since I have had a Christmas tree."

"Really?" Sans asked as he worked at untangling the lights. "What do you usually do?"

Gaster shrugged, leaning down to pick up a bright red ornament. "Oh, nothing exciting. I will go and visit Asgore for the evening." He hung the ornament on a branch with a smile. "Let me find a, er, plug for the li—"

"The King?" Papyrus interrupted. "You have Christmas with the King?"

Gaster blinked. "Er, well, yes. We usually have tea and chat while he knits."

"The King knits?"

Gaster chuckled and pulled at the collar of his sweater. "Here is the proof."

"Wowie," Papyrus said breathlessly, sockets starry.

Sans looked up at Gaster in (much quieter) surprise. Huh. Obviously he knew that Gaster and Asgore talked to each other, but he never thought they were actually friends.

"Imagine," Papyrus said wonderingly as he started stringing the (still tangled) lights, "Christmas with King Asgore."

At the same moment, Gaster and Sans looked at each other, the same idea hitting them both. Of course. Asgore should be invited over. It'd be the perfect Christmas gift! Gaster opened his mouth, but Sans was quicker.

"Y'know who we should ask about that? Santa."

Papyrus gasped. "You think he knows the king?"

"Oh, definitely."

"Then why are we still here?" Papyrus asked incredulously. "We might not have enough time!" He snapped his fingers. "Can we take a shortcut?"

"Not three of us."

Gaster waved a hand. "Go along. I do not mind waiting."

Sans shook his head. "No way, Gaster. I bet it's been ages since you've asked Santa for anything. You need to come along and see if he even remembers you."

As Gaster gave Sans an amused look, Papyrus—already going to the door—turned around worriedly. "Can Santa forget people?"

"You don't need to worry, Pap." Sans winked. "After all, you guys exchange letters three times a year."

Papyrus relaxed. Gaster looked at Sans curiously. "Three times?"

"Sure. One to ask for presents, one to thank him, and then he likes to check in during summer, to make sure Santa's doing all right. Hey, Pap, rem—" Sans trailed off as the door opened and Papyrus was already a figure in the distance. "Aaand he's off."

Gaster chuckled, nodding for them to follow him (though at a much slower pace.) "You know, he is a bit like myself when I was much younger. I used to be able to run from Home—er, The Ruins—to the Lab in just over fifteen minutes."

"Because you wanted to see Santa?"

"Because I was running late."

Sans laughed. "You ran late? Come on, Gaster, even I make it to my job on time."

"Yes, well, not all of us can...what is the term you used? Teleport."

Sans lifted his cheekbones. "Well, since you mentioned it..." he said, then teleported about 10 feet ahead. Gaster laughed and picked up his pace.

"You are a show-off, Sans."

"Me? Show-off? Never," Sans assured, then teleported forward again. This time, once Gaster caught up, Sans stuck his hands in his pockets. "So, uh, what did skeletons do for Christmas? Back on the surface, I mean."

"We did not celebrate it."

"What? Really?"

Gaster nodded. "Neither did monsters." His hands fluttered. "The human, the one the king and queen took in, it...er, they insisted we celebrate it down here." He let out a breath. "Much as I dislike humans, this did raise spirits even after the children died. So perhaps they are good for that." He half-smiled. "And anyway, monsters will look for any reason to celebrate." He looked down at Sans curiously. "Did your parents do anything for Christmas?"

Sans shrugged. "Well, yeah, but, uh, now that I think about it, I don't think they really knew what the deal was," he said with a little laugh. "But, y'know, they didn't want us feeling like we were missing out on anything. But my, uh, my dad always made the best hot chocolate. I have no idea what he put in it—I try to make it every year, but it never tastes the same."

Gaster looked down at the smaller skeleton for a moment, then asked, "And what do you and Papyrus do now?"

Sans winked. "Barge into unsuspecting scientists' houses, obviously." He chuckled. "Normally, it's Papyrus singing for hours before we call it a night. I get the presents downstairs—that'll be a cinch this year—and we have breakfast before watching whatever it is Mettaton puts out for Christmas." His cheekbones lifted. "Not exciting, but hey, it makes my brother happy, and that makes me happy."

Gaster gave Sans a small, warm smile. "Then that sounds quite exciting."

The crunch of snow signaled their entrance into Snowdin. Gaster looked around with a smile, hands clasped behind his back.

"I will say, Snowdin does seem more festive. I suppose that is why I enjoy this time of year so much," he said as they walked into town.

In the center of town, Asgore was seated by the tree. His beard and hair had been powdered white, and he wore a red suit and hat. Papyrus, long legs carefully angled to ensure maximum lap room, was already chatting with him. Gaster glanced down at Sans.

"Have you thought that perhaps it is time to tell him that Santa is just Asgore in a costume?" he whispered.

"If you can do it and keep your heart in one piece, be my guest."

"Hm, fair point."

Papyrus saw them approach and waved, immediately launching himself off of Asgore's lap. Sans nudged the scientist.

"Go on, Gaster, it's your turn," he said with a wink.

Gaster stared down at him. Sans nodded toward Asgore. After a moment, Gaster relented with a laugh. He walked over to Asgore, who seemed to be trying very hard not to laugh. Gaster was not nearly as successful. After a moment, he composed himself and leaned over slightly.

"Hello, Santa. I w—"

"No, you can't ask like that!" Papyrus called from the sidelines. "You have to sit on his lap!"

"He's right, Gaster," Sans added, "you absolutely gotta sit on his lap."

Gaster sent them an odd look over his shoulder; both brothers gave him a thumbs-up in reply. The scientist shook his head with a little laugh, then carefully maneuvered—his legs were longer than Papyrus', after all—to set himself down on Asgore's lap. He met the King's gaze very seriously.

"Santa," he greeted.

They stared at each other for a moment. Then, at the same moment, their composure broke and they burst out laughing.

After a solid minute of laughing, Asgore contained himself enough to ask, in his best Santa voice, "Ah, W.D. Gaster! It's been a long time since I've seen you. What would you like for Christmas?"

Gaster fought off another laugh. "Well, Santa, what I would like more than anything is for King Asgore Dreemurr to come spend Christmas Eve with me and these two fine young men..." He gestured to Sans and Papyrus. "...at the lab."

Asgore grinned. "Well, I think I might be able to pull that off."

Gaster grinned. "Perfect. And, er, one more thing." He glanced over at the brothers, then turned to Asgore and lowered his voice. "Can you still make your hot chocolate? The one you used to make for your children?"

A little flicker crossed Asgore's face, but he nodded. "Yes, I think so."

"Well...I think that would be an excellent surprise as well, if it is not too much trouble."

Asgore tapped his snout with a wink, then gave Gaster a hearty pat on the back (which nearly catapulted him into the snow) with a loud, "Ho ho ho!"

"Well, the King isn't going to invite himself," Asgore said. "I'd better go run by New Home and see if he's home." Once Gaster got to his feet, he shook the skeleton's mangled hand with a grin. "Now, don't be a stranger next time, W.D."

Gaster merely laughed and shook his head, then returned to Sans and Papyrus. Papyrus looked as though he might explode from excitement.

"Did it work? Is the king coming?" he asked.

"Oh, of course," Gaster assured. He motioned for them to start walking. "I have been around for a long, long time, and Santa has not disappointed me yet."

~

"Gaster, this isn't going to work."

"I think I know how to use a Bunsen burner, Sans."

"But for popcorn?"

"It is no different than a stove. Well, in principle, that is."

"Oh my god, is this how you cook?"

"Nonsense. Cooking takes too long. It is how I heat my tea, though."

Since coming back from their visit with "Santa," all three skeletons had been busy decorating the lab. The tree, while not necessarily pretty, was very decorated, and Papyrus was aggressively caroling as he strung tinsel over the equipment and whiteboards. Gaster, meanwhile, had thought it would be a good idea to string some popcorn to add to the decorations.

But all they had was Alphys' microwave popcorn. And the microwave, for reasons Gaster wouldn't say, was currently broken. So Gaster improvised; he poured the kernels into a cylinder, held it over the burner, and hoped for the best.

Sans was beginning to see how the scientist wound up with so many cracks.

A knock at the door gave him a good excuse to get away from the potential hazard. It slid open with a hiss, and Asgore, holding a bag and wearing a big smile, was standing just outside.

"Hey, Asgore. You're just in time to watch Gaster crack his skull again."

"This is perfectly under my control, Sans!" he called, giving the cylinder a little shake.

Asgore chuckled. "This is why I tend to make the tea when he visits," he said as he walked in. Immediately, Papyrus' head shot up over a whiteboard.

"Santa DID IT!" he exclaimed, scrambling over to the King's side. He bowed so hard he nearly fell over. "On behalf of the Snowdin sentries, I would like to say Mer—"

He was cut off as a loud popping filled the room. Gaster was dodging red-hot kernels of popcorn as they shot out like bullets, trying his best not to drop the cylinder in the process. Papyrus quickly spread out his arms to (barely) cover Asgore.

"Don't worry, Your Highness! I'll protect you!" Papyrus called as popcorn flew across the lab. Sans came back from the door just in time to be hit square between the sockets with an unpopped kernel. He immediately fell backwards to the floor.

"Sans!" both Gaster and Papyrus called. In a moment, Papyrus was at his brother's side.

"Are you badly hurt, brother?" he asked urgently, lifting Sans' shoulder's slightl. Sans lifted a shaking hand.

"P-Papyrus..."

"Yes, brother?"

"I...I just want you to know..."

"Yes?!"

"Even...even if you thought my jokes were corny, I couldn't ask for a butter brother."

Papyrus stared at Sans as the other skeleton started to laugh, then abruptly dropped him onto the floor and stood up.

"Aw, come on, that was a good one, Popyrus."

"DO NOT SLANDER MY NAME WITH YOUR PUNS."

As the brothers continued their usual fight, Asgore walked over to Gaster and pat his arm.

"How about I take care of anything cooking-related?" he said with a smile. Gaster looked up at him, then shook his head.

"My innovativeness is unappreciated," he said, then nodded toward the stairs. "The kettle is up there. I suspect it will be easier for you to use than graduated cylinders and Bunsen burners."

~

Once the popcorn was cleaned up, the night was quite nice and cozy. Papyrus was having the time of his life hearing Asgore's stories of fighting in the War and training Undyne. Sans and Gaster, on the other hand, were signing nearly exclusively—Sans still wasn't great with the grammar, but considering Gaster's bright expression the entire time, he didn't think the scientist minded.

But, of course, he was still prone to nodding off, especially after such an exciting day. Just as his head started to bob, a warm mug was set into his hand. He looked up in surprise at Asgore, who smiled.

"I have it on good authority that you and your brother have hot cocoa every year," he said quietly. "I hope you don't mind if I made it for you this year."

Sans' cheekbones lifted. "I'd have to be royally petty for that."

He took a sip, and his sockets widened. It wasn't like his dad's, but it was still good. Amazingly good. He looked up at Asgore, cheekbone's lifting again.

"Don't suppose you could just pay me in this?" he asked quietly, lifting his mug. Asgore chuckled.

"I could, but then it wouldn't be special, would it?" he said, then winked. "And most shops don't accept hot chocolate as currency."

"The king threw a snowball at you, Dr. Gaster?" Papyrus exclaimed, directing their attention over to the other two.

"He did. We had barely spoken, and he outright assaulted me during our expedition," Gaster said with a nod.

"Now hold on, Gaster, that's not how it went," Asgore said.

"Oh? Perhaps my brain is too muddled from a snowball hitting my occipital bone to remember properly."

"You're being a difficult old man is what's happening." Asgore leaned forward. "Now, listen, Papyrus, here's what really happened on our expedition..."

As they told the story—each interrupting each other—to a starry-socketed Papyrus, Sans settled down in his seat as he sipped his hot cocoa. A warmth that was not entirely from the hot drink filled his chest. This, he thought, was what he had missed for the past several Christmases.

~

"And do you remember, when I told you to give a speech for the University's first graduation?"

"Oh, god. It was hideous. Alphys, I think, has found a video of it. She keeps threatening to put it on, er, Undernet is what she calls it, I think."

"Oh, she wouldn't."

"No, but I think she likes having that sort of power over me."

"Well, surely one of these boys would know. Say, would either of you—" Asgore looked up to the brothers, and he smiled a bit. On the old sofa in the corner, both of them were fast asleep. "It looks like we've worn them out, Gaster."

Gaster looked up at them, and he smiled a bit. "Well, they were quite busy bringing joy. I am not surprised they are tired." He got up and lightly tapped on Papyrus' shoulder.

Immediately, he jolted awake. "What is it? Is there a human?"

Gaster chuckled. "No, no, we are quite safe. But it is getting late, and I am certain Santa will be coming soon."

Papyrus jumped to his feet. "You're right! Sans! We need to get back home!"

Sans mumbled in reply, sinking lower into the couch. Papyrus huffed.

"How are you always so lazy?" he asked. He pulled up his brother and slung him on his back. "We're going home, Sans! We need to be ready for Santa!"

"Hmmmmokay," Sans mumbled, not fully waking up.

Papyrus shook his head. "It is a very good thing I vouch for you to Santa." He turned back to look at Gaster and Asgore. "Merry Christmas, Dr. Gaster! And a very Merry Christmas to you, Your Majesty." He gave Asgore a deep bow that nearly catapulted Sans off of his back (not that Sans noticed), then turned and quickly exited the lab.

Gaster smiled, then turned to Asgore. "And you? Do you need to go home to wait for Santa?"

Asgore chuckled. "I think I have time enough for one more cup of tea." He got up and carefully picked up an Erlenmeyer flask that had been gently warming the tea over a burner to fill his and Gaster's mugs. "It's nice, isn't it?"

"The tea? Of course it is; you were meant to be a tea maker."

Asgore chuckled as he poured the tea. "No, I mean spending Christmas with family."

Gaster sent Asgore a dubious look. "You know better than anyone that I am not related to them."

"You don't have to be related to be family," Asgore corrected gently as he handed Gaster his mug.

Gaster blinked, then looked down at his tea. He smiled a bit and shook his head. "I do not quite agree with you," he said after a moment, but he smiled wider as he took a sip of tea. "But...I do think this was the best Christmas I have ever had."