Of all the strange things that Baymax had experienced, being stuck in a tree ranked fairly high on the scale.

It really shouldn't have happened; he should have been paying more attention. But Hiro had begun wriggling around on his back for a better view of something, and Baymax - trusting in his internal map of the city to guide their flight - had turned his head to look at the colored light display he was pointing out, and by the time his proximity sensors sent a warning blaring through his awareness it was too late.

However improbably, he was now suspended nearly two hundred feet over the streets, tangled in the branches and wiring of a massive light-strung pine tree.

"Hiro." He searched briefly for words to express his bewilderment and decided bluntness was his best option. "There is a tree."

Hiro giggled, chin resting on Baymax's shoulder.

"You noticed, huh? Hold still."

Baymax obligingly kept his body as still as possible, turning his head to watch Hiro as his friend left the relative safety of his back. The tree, he realized, was not real - that is, not a genuine pine tree but a surprisingly convincing fabrication of metal and fiberglass - which at least explained how it had sprung up in the space of a day. Aside from the strings of lights it was littered with decorations - mainly globes, some as large as Baymax himself or even larger - and some twenty-five feet above their perch there appeared to be a large eight-pointed star.

Once the lights were lit, the tree would be impossible to miss; it should have been impossible even dimmed. Baymax felt an unfamiliar, almost squirming form of distress that he quickly identified as embarrassment.

"Why is there a tree?"

"Hm?" Hiro looked up from his work - he was using his magnets to cling to a metal branch, trying to dislodge a cable that had somehow wound its way around Baymax's wing. "Same reason there are lights. I mean, more than usual. They're the city's Christmas setup."

Baymax blinked. The word tickled something in his memories, and embarrassment melded with more familiar frustration when he realized he couldn't quite catch it. Something he'd not-quite-heard while in standby, then; such things usually weren't important.

It felt important this time, but pursuing it too aggressively usually meant increased frustration. Baymax instead returned his full attention to Hiro.

There was no call to be distressed; Hiro's magnets kept him safely on the tree, and Baymax had at least enough reach and mobility to catch him if he misjudged. Hiro would free him, and Baymax would bring Hiro safely to the ground, and he could examine this strange turn of events more thoroughly later.

Then Hiro hailed the others to relay the problem to them; as Wasabi's groan and Gogo's snort and Honey Lemon's stifled giggle and Fred's outright guffaw echoed through his helmet, Baymax decided that perhaps there was call for the 'embarrassed' variant of distress.

Baymax could have simply downloaded an explanation for the giant tree and other oddities cropping up around the city (and their own home), but he had learned that it was often more interesting to ask Hiro.

"Christmas is..." Hiro paused. "Well, technically it's a religious thing I guess. Not so much for us. Mostly you spend time with friends and family, give presents, eat a lot of food."

"We spend most of our time with friends and family." Baymax paused. "And you and Fred in particular consume alarming quantities of food on a daily basis."

"I'm a growing boy." Hiro waved a hand dismissively. "Anyway there's special food. Lots of baked stuff. You know, Christmas cookies."

Baymax tilted his head.

"No - I do not know. How do they differ from normal cookies?"

"Well, uh..." Hiro frowned. "I guess... technically they don't? I mean, some are more common this time of year. Uh, you know - like being in season?"

"I see." Baymax nodded. "And the time together differs because...?"

"It uh... doesn't really either." Hiro grinned. "I mean we're pretty much all together... I guess that more applies to people who live far away and come visit... and you do stuff like tell stories and exchange presents... and yes, I know, we give each other stuff all the time but there are a couple times of year where everyone does and this is one."

Human strangeness, Baymax concluded, and wondered if the whole thing would make more sense if he did simply look it up. Still, thinking about it did seem to put Hiro in a pleasant mood, and the decorations were interesting when they weren't providing unexpected obstacles.

"Will you be making or obtaining special gifts for the occasion?"

"Yeah, I started months ago!"

Already? But Christmas isn't for another five months.

Baymax blinked at the echo of not-quite memory, seizing it for closer examination as Hiro flopped to start pulling things from under his bed. The voice was only vaguely familiar, and Baymax was uncertain whether it was because his awareness was limited in standby or because the speaker had been unfamiliar.

It was important. Baymax was somehow certain of this, and however his programming and emotional responses grew he was also certain he was not given to human irrationality where convictions were concerned.

He needed to determine just what it was he was remembering.

Hiro had gone very still amidst the half-finished projects he'd pulled out of hiding, and even without a scan or a clear view of his expression Baymax could sense his sudden tension. The not-quite-memory would have to wait; he settled awkwardly beside Hiro, laying a hand on his back.

"Hiro?"

"This was Tadashi's. For Tadashi I mean... I tossed it back here and... forgot..."

Baymax caught the break in his voice and shifted to rest his hand on Hiro's shoulder instead, squeezing gently; Hiro reached up to catch hold of his finger, clinging, and Baymax carefully shifted until he could pull Hiro into the crook of his other arm.

The small robot in Hiro's hand looked as if it hadn't been touched in months, dust clouding the surface and clinging to wiring in fluffy clumps. He was silent a moment, breath hitching suspiciously, before he leaned into Baymax with a trembling sigh.

"I was making a helper bot for his lab. You know - files and stuff. I mean... probably not as good as what he could make himself, but..."

Baymax hesitated, uncertain of how to proceed.

"I do not believe Tadashi would have thought so," he said after a moment. Hiro gave him a wobbly smile at that, nodding.

"Yeah... he would... would have..."

He held the robot close to his chest with a tiny, choking sound Baymax knew well, and he carefully tightened his hold on Hiro as the boy curled as if trying to burrow into him. Baymax kept still as Hiro's fingers closed tight around his hand and his thin body shook with sobs, and he hummed to Hiro in a soft, tuneless drone that his companion nonetheless seemed to like.

"Will you finish it?" Baymax asked quietly after a few moments. He wasn't certain the question was helpful or even appropriate, but Hiro looked up at him with another thin smile and nodded.

"Yeah. That's... I will. That's a... a good idea."

He took a deep, trembling breath and slowly relaxed, still holding the unfinished robot close as he started sorting through the other projects scattered around them.

"Anyway, um... here's what else I have..."

Within a few days another pine tree appeared in the entryway of Fred's house, and a day after that a third tree appeared in the Hamadas' living room. The tree in Fred's house was genuine, the one at home another fabrication, and of course both much, much smaller than the city tree. Baymax vastly preferred the small trees over the massive one, and only partly because he hadn't gotten stuck in either; the real charm was in the group crowding around to decorate them, bickering good-naturedly over placement and retelling or simply making up stories about various ornaments.

Fred had insisted Hiro place the star on his tree, and Hiro had eagerly bounded up the ladder to do so before calling for Baymax to catch him as he leaped down; at home, Hiro offered the star to Baymax.

"It was... kind of always Tadashi's job," he mumbled, glancing up at Baymax with a bleary half-smile before looking down at the star in his hands. "But since... I don't... maybe you..."

The implication was not lost on Baymax. He reached to carefully take the star from Hiro and held it up to study, noting delicate wire studded with small faux crystals winding around the points before he looked at Aunt Cass; he wasn't certain how to read her expression - a strange, small smile, brows knit and eyes brimming - but she nodded and murmured a go-ahead and he turned to set the star atop the tree as quiet, warm satisfaction and mild, worried distress both crept through his processes.

It was pretty, he decided; human strangeness was often pleasant even if it was inexplicable, and the fond looks Hiro and Aunt Cass gave him through their barely-held tears chased away all but the smallest spark of worry.

A part of him suspected he was a poor substitute, and it was a strange shade of worry he didn't know how to process. Still, his two humans looked happy enough after a moment to compose themselves, and he was willing to content himself with that.

The idea that he was close to remembering something important persisted as the season wore on.

Baymax endured the strange customs of Christmas with a mixture of curiosity and bewilderment, patiently allowing Honey's attempts at stuffing him into a handmade sweater and struggling to follow the tunes Hiro tried to teach him and marveling at the perfect absurdity of exchanging romantic gestures beneath toxic plants. He listened to roving carolers and helped decorate cookies and watched wrapped gifts pile up under the tree.

He noticed his friends' moods suddenly dampening from time to time, more often than they had in months, and often found himself gathering one or more into a careful embrace; a time that was built around the idea of pulling humans together was an obvious obstacle, and Baymax was at a loss trying to work through their balance of cheer and sorrow.

He needed to remember whatever it was that kept prickling at him.

"Well, that takes care of everyone."

Baymax blinked at Hiro's brisk tone, looking at his friend; Hiro was sitting on the floor with his now-completed gifts spread around him, satisfied smile lingering even as he traced his fingers over the robot meant for Tadashi.

That's everybody taken care of.

Baymax blinked again. That was it, almost; he was close.

Then Hiro's wistful sigh caught his attention again and he shuffled closer to peer down at him.

"Are you all right?"

"Yeah... yeah, I'm good." Hiro rubbed hard at his eyes and then grinned up at Baymax, gesturing for him to sit. "Here, look - I'll teach you to wrap presents."

Baymax suspected that this was at least in part because Hiro didn't want to do it all himself, but he kept that observation to himself and settled in.

An hour later Baymax was covered in tape scraps, draped with ribbon, and wearing a large, shiny red bow Hiro had stuck on his head, but the wrapping was finished and Hiro was gathering the messy bundles into his arms.

"Okay, should be about dinner time so I'm gonna pop these under the tree and then see what Aunt Cass has ready... coming?"

"No," Baymax said after a moment. "I will... clean up the mess we have made. Perhaps I will join you downstairs afterward."

"Oh." Hiro nodded. "Good idea, thanks... see you in a few then."

Baymax nodded, watching Hiro head out; once he'd heard him go thumping down the stairs Baymax turned his attention back to the scattered wrapping supplies, studying them a moment before turning to Tadashi's closed-off half of the room.

"Hey, Baymax! How long's it take to clean up paper? Aunt Cass wants to take the family picture now."

Baymax looked up from his handiwork, blinking as Hiro popped into the room.

"My presence is required?"

"Of course it is, dummy." Hiro punched his arm, grinning. "You're part of the family, aren't you?" He laughed, the sound trailing off as he glanced at the pile Baymax had arranged on his bed. "Hey, what's all this?"

He picked up one of the wrapped gifts, brows raising as he read the clinically neat writing on the tag.

"To Hiro, from... from Tadashi...?"

He looked up at Baymax, who shuffled slightly and made a small, apologetic hum.

"I remembered," he said after a moment. "I was in standby. But Tadashi brought all of this into his work area, several months ago. I can hear in standby, more or less - but I do not always fully record what occurs unless I am directly called."

"Oh," Hiro said, his voice a bare, breathless whisper before he cleared his throat. "Oh, uh... yeah. That... that makes sense..." He looked over the gifts, a smile similar to the one Aunt Cass had given Baymax over the star creeping onto his face. "So... these..."

"These were in Tadashi's personal effects. It was not difficult to determine which gift was meant for which person."

"Yeah, probably wasn't. Y'know, we... never went through his stuff after," Hiro said absently. "At first we... just couldn't... and then... stuff happens, guess it got... lost." He looked up at Baymax again and blinked hard, tears spilling over his cheeks as he smiled. "Thank you."

Baymax gave him a small, pleased squint in return, then hesitated a moment before speaking again.

"Hiro. I know I am... a poor substitute-"

"Stop." Hiro's voice was low and gentle as he set the gift down. "You're not a substitute. For anything - okay? You're just you." He reached up to wrap his arms around Baymax, face half-hidden against the robot's chest. "I love you. Okay?"

The grain of worry still laced through Baymax's thoughts dissolved, and he gathered Hiro up to hold him close. They remained that way a long moment before Hiro released him, patting his shoulder lightly.

"Now come on. Hamada family portrait first - and that means you too. Got it? And then the others are coming over for a big family photo. Which also includes you. Got it?" He waited for Baymax's nod and grinned, moving to gather up the gifts. "Now come on!"

The robot nodded again, watching Hiro hurry out of the room with the gifts he could carry.

Then Baymax gathered up the rest and went downstairs to his family.