Taking a little break from TWOHHHIII (dang that's my longest acronym yet), and posting a one shot. This is based off a bonus feature of httyd 2, called Hiccup's Inventions in Flight, where we see original concept art for Toothless and Hiccup's prosthetics. I think it's really interesting, at least on Hiccup's side, that there was originally more uses for his leg than we see in the movie, and I thought it would be fun to write the backstory for how Hiccup made them. Thus, this drabble was born!

"I might make a few tweaks…" That was what he'd said four years ago, upon waking up to find almost half of his left leg had been replaced by wood and metal. In truth, the comment was purely said as a means of trying to avoid how he was really feeling in that moment, since humor tended to be an escape of sorts. And with a fifteen year old whose mind was still very much trying to process just what exactly was going on, those were the words he'd ended up with. Those mentioned "tweaks" were never actually part of the plan.

And for four years, that remained true; the only change Hiccup ever made to his leg was fixing the length. And Hiccup still wasn't planning on ever changing anything else.

But now, with the Dragon Hunter War behind them, everyone living on Berk once again, and no foreseeable fighting in the future, Hiccup found himself with a superfluous amount of free time. For a while, it was just an excuse to fly with Toothless for the better part of a day, but now, Hiccup was facing something he never thought he'd face: boredom.

He loved flying with Toothless; there was absolutely no doubt about that. But after weeks and weeks of the same routine, the fun of flight was beginning to lose its magic. He could tell Toothless was feeling it too, as the Night Fury was waking up later and later, as if sleep was the best idea for passing time.

So, it was this afternoon, as the pair was getting ready to go out on yet another flight since there was nothing better to do, that it hit Hiccup. The idea came as he clicked Toothless' tail into position for the millionth time, and wondered if there was any way to make that habitual movement feel new. In fact, the inspiration struck so hard that Hiccup simply jumped off Toothless and began sprinting back home (forcing the very confused dragon to run after him).

By the time Toothless had made it inside, Hiccup was already at his desk, furiously sketching and muttering nonsense that only he could understand. "If I just put this piece here… build a pulley there… tweak that connecting rod… adjust the stirrup- no, remove the stirrup… And add hand controls! Yes!"

"What are you doing?" Toothless asked, though his human didn't seem to hear him; he was far too focused on the parchment in front of him. So, Toothless stuck his head into Hiccup's field of vision, forcing him to notice.

"Not now, Bud," Hiccup said, gently nudging Toothless' head away. "I need to get this down." He scratched his charcoal across the paper a few more times before stopping, a perplexed look forming on his face. "Hm. But what to do about that…"

Toothless craned his neck over his rider's shoulder, getting a look at what he'd drawn. It looked like his saddle and tailfin, but there were notes littering the picture. Then, Toothless noticed that it looked a little different; the left side was completely redesigned. Toothless tilted his head, as Hiccup continued to tap his writing utensil on the desk. Toothless just watched, as the gears in his rider's mind turned, before he suddenly jumped up. "That's it!" He scratched Toothless' head, grinning. "Hope you're up for something different, Toothless. 'Cause we've got tests to run, and designs to perfect!"

Toothless blinked; tests. Every "test" his human ran with past inventions only ended in disaster. But this time, things were different. This time, Toothless was one of the subjects.

It was going to be an interesting few weeks…

...

Word quickly got out around Berk that Hiccup was up to "something." No one knew exactly what it was, but it involved frequently seeing the boy, wearing a ridiculous grin, and his dragon at the forge. The villagers brushed it off, because Hiccup had always been "unusual", but those closest to him were getting suspicious.

Gobber, who obviously was also at the forge a lot, had tried several times to sneak a look at the project, only for Hiccup to hide it from view and glare. He took it home every night, so Gobber couldn't even get a peek when no one else was around.

Stoick became aware that his son was missing much more often than before, hardly even making it to the meals they set time aside to share. He also noticed a couple of weapons that had previously hung on walls had mysteriously disappeared.

But out of everyone, Astrid was the most suspicious of them all. She would often stop by the forge at odd times, trying to catch her boyfriend off guard. Yet, somehow, he always seemed to know when she was coming.

"I know you're up to something, dragon boy," she said. "You won't be able to hide it forever!"

"Please, Astrid, execute a little trust," Hiccup replied. "When have I ever hidden things from you before?" Astrid's eyes narrowed, in a 'are you kidding me?' look. "Nevermind, don't answer that," Hiccup said. "Just believe me when I say that if I was working on something, which I'm not saying I am, I would want you to wait until it's ready for you to see it."

Resigned, Astrid just exhaled and walked away. The moment she was gone, Hiccup pulled the tarp off his project.

It was coming along nicely. He had built a new mount for the left side of Toothless' rig (out of melted metal from one of his dad's display swords, Hiccup was afraid to admit) and his idea for the rope to be moved by lever rather than pedal seemed to be working. The pulleys didn't require a ton of adjustments, just in the place where they connected to the new lever. And, when Hiccup tested the rod, it moved just like he was imagining.

"Whaddya think, Toothless?" He asked, getting a skeptical grunt in response. "Oh, come on, you'll never know if you like it unless we try it." Toothless stared blankly at his human, an unamused frown on his face. "Please? Just a little test run?"

"Fine, but no tricks," Toothless conceded, letting Hiccup work on attaching the new rig to his saddle. Once he was done and up on Toothless' back, Hiccup realized his next problem.

His prosthetic.

Toothless' original saddle design locked his metal foot in place so he could move the stirrup, but his new design had no way of keeping him attached. Still, never one to be turned away from trying, Hiccup set the flat end of his foot on the lever, and pushed it forward. Behind them, they heard the telltale sound of Toothless' fin opening. Both boy and dragon looked back, and Toothless gave Hiccup a pleased glance, before spreading his wings for takeoff. Perhaps he had too little faith in his human; it seemed like everything was working.

Which it was… on Toothless' end.

However, Hiccup had failed to anticipate what he would do when the fin needed to be closed, and after a moment of panic, the two found themselves digging a ditch in the snow.

"Well that went wonderfully," Hiccup said, staring at the sky from his position flat on his back in the snow. A second later, Toothless padded up to where his rider had been thrown, leaning over him and glaring. Hiccup gave the Night Fury a guilty smile, to which Toothless just kicked a load of snow on his head.

Thoroughly frozen, Hiccup got back up, going to inspect the prototype saddle. "Maybe I should have thought about how this would work with my leg earlier…"

"You think?" Toothless grumbled. As much as they were used to it, he didn't appreciate being crashed into the ground due to his human's lack of foresight.

"I bet I could make some type of clip or something…" Hiccup said, hopping onto Toothless again and setting his prosthetic back on the lever. He studied it for a second, before an almost insane smile crept across his face. "Or maybe…"

"Please don't," Toothless said dryly, hoping his human would pick up on his tone.

"Maybe it's not the saddle I should tweak…" Hiccup finished, and Toothless huffed. "C'mon, let's get back to the forge." He nudged Toothless' side, only for the Night Fury to look back at him with narrowed eyes. "Walking, Toothless. Not flying."

"Finally, some sense…"

...

Hiccup had no ideas. As much as he tried to push his mind to create a new design, he just couldn't think of anything. Gobber's original design was already so well made, and served its purpose as best as Hiccup could've asked for. He sighed, deciding that maybe a quick walk would spark the imagination. He always thought better while moving, anyway.

Hiccup pushed open the front door, a chill running through him at the exposure to cold winter air. He pulled his coat higher, then started out into town.

The rest of Berk was fairly busy, as Vikings didn't tend to slow their activities much just because of the cold. Hiccup smiled, seeing a Monstrous Nightmare nearby with its body aflame, melting the snow off pathways. He could never truly get over how much the town had changed because of him and Toothless...

"Augh!" Hiccup blinked, unsure of what had just happened, before realizing he was now staring at the sky.

"Hiccup! Are you alright?" Astrid's voice yelled from somewhere nearby. After a moment, a hand appeared above him, and she pulled him to his feet.

Hiccup looked back, noticing a stretch of ice with a clear mark where his metal foot had slipped. "Oh," he said.

"'Oh?' That's it?" Astrid commented. "You took quite a fall."

"I wasn't paying attention, I guess…" Hiccup responded, thoroughly embarrassed now that he'd figured out what happened. He rubbed a sore spot on the back of his head; he must have hit it.

"Unsurprising," Astrid laughed. "Too busy thinking about whatever it is you've been hiding from us for the past week."

"What I've been- no, of course not!"

"Yeah, sure…" she teased. "Well, I'll let you get back to 'not thinking about it'. Just watch where you're going, alright?" She gave him a quick kiss on the cheek.

"I wouldn't do anything less." Hiccup waited for Astrid to disappear around the corner before turning back to the ice. "Hm."

Maybe that was something.

He'd never really thought about it before because taking a few tumbles during winter just seemed like it was inevitable. What if it wasn't? What if he could make a foot that kept traction on ice?

Of course, then it wouldn't be very good for when the weather was warm… it'd probably get stuck in mud. But what if he made a few different feet for different situations?

...Including flying?

A grin crept onto Hiccup's face; he finally had an idea.

...

"What do you think, Bud?"

Toothless looked over his human's sketches, giving him a grunt in response. He'd accepted that Hiccup could not be stopped in this idea, but still thought it didn't need to happen in the first place; their flying gear was fine how it was before.

"Come on, you know I need more feedback than that," Hiccup said.

"You think it's smart to have three different legs?" Toothless relented. To make sure Hiccup understood, Toothless dug in his storage chest, pulling out his spare legs and lining them up.

"I don't get it."

Toothless held up one leg, then switched it for the other, then back to the first.

"You think it's too much hassle?"

Toothless nodded.

"I see your point… we switch from flying to walking quite a lot, it could get tiresome to change legs all the time…" Hiccup tapped his desk thoughtfully. "What if I put all the feet in one design?"

Toothless snorted; now that was a crazy idea. And if his human's past experiences were anything to go by, then it just might end up working.

"The question is, how do we make it easy to switch…" Hiccup mumbled, more to himself than Toothless. He yawned; it was late and he really should be getting some sleep. Astrid was always yelling about how he neglected personal needs when he was in an inventing phase… he could pick back up on it in the morning.

Hiccup settled into bed, closing his eyes and mumbling a "good night" to Toothless, as his mind wandered elsewhere.

He thought about life back on the Edge, and all the adventures they had. Living alone, finding new lands, discovering new dragons, fighting new foes... Those were some crazy days, with the Dragon Eye; who knew a little rotating tool could cause so much chaos?

Hiccup's eyes snapped open.

The Dragon Eye was a super versatile piece of equipment, and it changed by rotating different pieces. What if Hiccup could design his new prosthetic in the same way?

Suddenly wide awake, Hiccup leapt out of bed, getting a startled screech out of Toothless in the process. He just had to get this idea down!

"Hiccup! Sleep! Now!" Toothless scolded, only to be thoroughly ignored.

Hiccup wasn't going to be sleeping anytime soon.

When Toothless opened his eyes the next morning, he was displeased to see his human still at his desk (though he wasn't exactly surprised).

"Toothless! Finally, you're awake!" Hiccup exclaimed. "I've been up all night, and I think I have something special here!'

"It better be," Toothless grumbled, walking over to his rider and looking at his work.

"I was thinking about the Dragon Eye, and figured out a way to get all three feet into one leg. As for the ice foot, that'll have to be moved manually, since I don't imagine it being used as often. But see this? A central spring connects the everyday walking and riding feet, so when I push the release, it'll bring one down and push the other back. The secret is in how this piece rotates, so one foot can be retracted while the other is moved out. Thus, easy switching! Pretty genius, no?"

Toothless tilted his head. He did have to admit, it was rather smart… but he was still mad at Hiccup for not sleeping. So, he crooned approvingly before nudging his human toward bed.

"Toothless, I can't sleep now! I need to get started on building this!"

"No." Toothless pushed his friend harder, but Hiccup was using all his strength to fight back. Finally, the Night Fury bit down on Hiccup's shirt, and began dragging him toward bed. As much of a fight as Hiccup put up, he was no match for a dragon. Toothless plopped his human in bed, then laid himself across Hiccup's legs, so he couldn't get up again. "Stay. Sleep. Now." Hiccup huffed, crossing his arms in a display of defiance. Still, Toothless refused to move.

"You're difficult," Hiccup said, allowing himself to settle into bed. Toothless hummed in victory, smiling smugly. After a moment, Hiccup spoke again. "For real, though, I can't feel my legs. Get off." Toothless narrowed his eyes, skeptical. "I promise I won't try to escape." Toothless looked his friend over, deciding he looked too tired to be able to do much anyway. So, he relented, sliding off the bed, but giving Hiccup a look that said 'I'm still watching you.' His rider didn't see it, however; he was already fast asleep.

...

Astrid poked her head into the forge, only to find that, once again, Hiccup had somehow anticipated her arrival and hidden whatever it was he was working on. How did he keep doing that? He must have had a dragon spy watching for her or something…

"I already told you, milady. If I was working on something, and I'm not saying I am, I would want you to see it when it's done," Hiccup said, arms crossed and leaning defiantly against the workbench.

"Come on, Hiccup. I'm your future wife! Just tell me already!" Astrid gave up on trying to stay hidden and made her way inside. "I've already seen you and Toothless crash several times, so I know it has to do with some kind of flying thing."

"And I've already said that those crashes were completely coincidental and not at all related to the project that may or may not exist. The fact is, sometimes Toothless is just clumsy." At that, Toothless whacked his human in the back of the head with his tail, growling. "...By which I mean sometimes I'm just clumsy," Hiccup amended, glaring at his dragon before turning back to Astrid. "Now please, if you'll be ever so kind as to leave, Toothless and I have things to do."

Astrid glowered at him, but Hiccup refused to give in. Finally, she huffed in defeat. "Fine. But I still know I'm right." She pointed a finger at her betrothed before turning and leaving the forge.

Once the sound of her footsteps retreated, Hiccup grinned and kneeled down, pulling his project out from under the workbench. "Finally, I thought she'd never leave…" He looked back up, presenting his finished prototype to Toothless. "Ready to test the new and improved leg?"

"All up to you…" Toothless rolled his eyes. "I'm not part of this one." He settled back on his haunches, waiting for the inevitable failure of a test to come.

"Please Toothless, contain your enthusiasm." Hiccup adjusted his position on the floor to untie his current prosthetic. "Now, when I make the final version, I think I'm also going to add a piece to my pantleg, like a release switch or something so I don't have to use rope anymore. But this should work for a test." Toothless just continued watching with half lidded eyes, until Hiccup had tied the new leg on. "Come here for a second, Bud." Toothless did, and Hiccup used his saddle to get to a standing position. "Okay, so far so good. I think it's a little short, but I can fix that. What's most important is how it handles weight…" He closed his eyes, taking a deep breath and stepping forward- only to fall flat on his face.

Toothless huffed in laughter, while his bemused human got back to his knees. "I guess the answer is… not so well." He looked down, only to see that his invention had gotten stuck between positions. "Maybe I made the trigger for switching feet a little too sensitive." Toothless snorted again. "Oh be quiet, it's not like you could any better."

"I don't have hands," Toothless replied, bopping his human's head with one paw.

Hiccup pushed his dragon's leg away, glaring at him, though he wasn't truly mad. "I get it, no need to rub it in!" He pulled off his prototype. "Well, I guess it's time to make a few more tweaks."

"To what?" A voice said from the front of the forge.

Hiccup kicked his project away, turning to see Astrid back at the counter. "Nothing!" He got back up, trying to lean nonchalantly against Toothless.

Astrid raised a brow in suspicion. "You sure? Seems like something's missing," she said with an amused smile.

Hiccup's eyes widened at the realization he hadn't had time to put his old prosthetic back on. Still, his mouth was about two steps ahead. "Well then, I don't know how to tell you this, Astrid, but it's been missing for five years."

Astrid rolled her eyes and turned away. "You can't hide forever, Haddock!"

...

Today was the big day. Hiccup had spent the last two weeks working tirelessly to perfect his designs, and now, they were finally complete. He'd told Astrid to meet him at the forge at midday, and the sun was getting close to its peak.

"Stay still, Toothless! I can't work with you moving like that!" Hiccup scolded his dragon as he struggled to get his new saddle on.

"I still think our old gear was perfectly fine." Toothless sat back, but made sure his displeasure was known.

"Come on, Bud, I promise you'll like it when we get flying. We'll be able to do even more crazy tricks and stunts with this new gear."

"That's just what I'm worried about," Toothless grumbled.

"Oh please, you know deep down you love those."

"Until I have to save your idiodic butt from certain death."

"Stop looking at me like that. Astrid will be here any minute and we both need to be ready."

"Fine…" Toothless turned away, letting his human finish attaching his saddle.

"Alright, looking good, Toothless! Now that just leaves me." Hiccup sat on one of the stools, getting to work on switching out his leg. He'd sewn a piece into the end of his left pantleg that the new prosthetic would attach to, and an almost giddy smile escaped him when he heard it click into place. "Okay." He got to his feet, taking a moment to adjust to the different feeling, before grinning at Toothless. "Look at that. I think I like it better already. And…" He swung into Toothless' saddle, pressing the button to swap from walking to riding feet. "It works!" Toothless hummed happily at his human. Maybe new didn't mean bad after all. Besides, if his human was this excited, then it was all worth it to Toothless.

"Hiccup? What did you want me here for?" Astrid's voice asked from the front of the forge.

Hiccup nudged Toothless forward, and he walked out of the building, coming to a stop just beside her, proudly displaying his and his rider's new gear. "Care to fly with us?" Hiccup held out a hand, a ridiculous grin on his face.

"That's what you were working on all this time?" Astrid exclaimed. She leaned down to examine his handiwork. "It looks so nice! What does it all do? Why didn't you just tell me this is what you were making?"

"Because you would have been an even worse critic than Toothless," Hiccup joked. "Now answer me!"

Astrid laughed, then took Hiccup's hand. "I would love to fly with you." She swung into the saddle behind him, and Toothless took off.

Once they were high above Berk, Astrid wrapped her arms around her boyfriend, laying her head on his shoulder. "I'm so glad this is all you were doing," she laughed.

"What's that supposed to mean?" Hiccup asked, sharing her laughter.

"For a while I thought you were trying to build DragonFly 3…" She chuckled. "Now that would have been a disaster…"

"Yeah…" Hiccup replied. "A disaster for sure…" But try as he might, he couldn't get the thought out of his head.

Looks like he and Toothless had a few more tweaks to make.

If I'm being honest, I really like the energy i made between Hiccup and Toothless in this one haha. I love it when they riff off each other... even though Toothless always wins in the end XD. I hope you all enjoyed! I tried pretty hard with the humor and relationships between the characters :D