Author's Note: Given the wide variety of Hijack AUs on Tumblr (Tarzan, Anastasia, Corpse Bride, etc.), I'm glad you guys find this interesting enough to read. Thank you very much for your reviews, favorites and follows. They make me so happy :)

Anyway, thought I'd mention this: Hypothesis follows the single-player campaign of Portal/Portal 2 with some elements taken from the co-op campaign. Of course, certain things will be tweaked to accommodate the crossover, but otherwise I hope to do the respective fandoms justice. Still, please do let me know if you feel I'm taking too many liberties or making things too OOC. I'd hate to disappoint.

Disclaimer: I do not own Rise of the Guardians, How to Train Your Dragon or Portal/Portal 2.

Hypothesis

Chapter 2: Meeting

:: Today, you will be testing with a partner. ::

Jolted roughly when the lift came to an abrupt stop, he let out a startled yelp when the floor suddenly opened up beneath him and dropped him onto another platform below. Picking himself up with a grunt, he palmed the clear glass walls surrounding him, finding himself trapped in a tall cylindrical tube. Before full-blown panic could set in however, a tapping noise to his right caught his attention and he turned his head to the side to find another test subject in the tube next to his, smiling excitedly.

:: Please wave to your partner. ::

The white-haired boy waved at him cheerily, flashing his teeth in a wide grin. He raised his own hand to mimic the action (admittedly with less enthusiasm) and managed a weak half-smile back. The smile turned into shocked gasp when the floor opened up beneath them again, sending them both to the next platform below.

While he wobbled slightly in an attempt to regain his bearings, the other test subject seemed unfazed by the sudden drop, landing on sturdy feet and laughing silently in anticipation of the next instruction.

:: The upcoming tests require you to work together as a team. To facilitate collaboration, both of you have been equipped with a laser tool. ::

Green light flashed somewhere near his left wrist and he glanced down to find a small laser pen mounted onto the side of the cylinder. He picked it up carefully, examining the device with curious eyes.

:: Green, please use your laser tool to select your favorite animal. ::

Several panels flipped open outside the tubes in front of him, revealing a three-by-three grid containing the silhouettes of nine different animals. If the color of their jumpsuits were anything to go by, he guessed that he was the one being addressed. Pressing the button on the non-operational end of the laser pen, a narrow beam of green light shot out and he aimed it towards the shadow of a snake in the middle of the grid.

:: Good. Blue, please observe your partner's favorite animal. ::

Ice blue eyes focused on the selected panel before flicking back to him and sending him a wink, as if conveying a quick note of appreciation towards his choice. He barely had time to respond before the floor yawned open again, dropping them onto the next platform.

:: Good. Blue, please use your laser tool to select your favorite element from the periodic table. ::

The panels flipped open once more, this time displaying nine different elemental symbols. He watched as the other test subject activated his own laser pen and cast a blue light on the top right panel, circling the selected symbol enthusiastically.

:: Really? Okay. Green, please observe your partner's… interesting choice. ::

Hydrogen, atomic number 1 and mass 1.008. Nothing special, but he gave his partner a half-hearted thumbs up in acknowledgement nevertheless. The floor opened up one last time, depositing them at the start of a test track.

:: Your laser tool can also be used to indicate to your partner where you would like them to place their portal. ::

He followed the corridor down towards the next area, finding himself in a larger room with a white handheld device mounted on a holder at the far end. There was a large gap in the middle of the room, splitting the area in half with the holder located on the other side. It was too far to even consider jumping across, he thought as he peered over cautiously. One look immediately told him that the pit was too deep to climb out of if he fell in. He shrank back warily, stepping well away from the edge.

Looking over to his left, in a room almost identical to his but separated by a thick glass wall, he noticed the white-haired teen facing the same problem.

:: For the sake of this test, I will pretend to be your partner. Using your laser tool, please indicate where you would like me to place your two portals. ::

A quick look around the room was all he needed to determine where would be a suitable entrance and exit. He shined his green laser on the white wall next to him before redirecting the beam towards the slanted panel hanging somewhere above the platform where the device holder was situated. Almost immediately, two green portals appeared at the indicated locations.

He jogged towards the portal on his right and jumped in, bracing himself for impact as he fell through the other portal and landed on the platform. Dusting himself off, he plucked the handheld device from its holder, causing the mechanical arm to lower itself into the open hole in the platform and disappear.

Turning the portal gun over in his hands to get a good look at it, he tried to figure out its mechanics as he located the dual triggers on the grip, hidden beneath the white shell protecting the device. There were three claw-like appendages protruding from the body of the long black barrel pointing forward, and the operational end of the portal gun glowed a faint green.

:: Green is first to acquire a Portal Device. ::

A whoop of success sounded from somewhere behind him and he peeked over his shoulder to see his partner leaping out of his own blue portal, landing on the platform in the other room to retrieve his portal gun.

:: Blue now has a Portal Device. Finally. ::

Smiling, he caught the white-haired teen's eye and sent him a congratulatory thumbs up, receiving another brilliant grin and a wink in reply.

:: Each portal gun may create two self-contained portals. Please test your device by portaling to that ledge. ::

Turning his attention back to the task at hand, he continued down the next corridor, firing his two green portals where needed to get himself up onto the higher levels of the room.

Despite operating on seemingly different test tracks, it soon became clear that they had to work together in order to reach the end. The whole place was connected somehow and they ran parallel to each other, stepping on giant red buttons individually to allow the other passage into the next section. There were areas where they had to fire portals into each other's room, accessing surfaces where their partner could not reach on their own. Other parts involved pressing small red buttons mounted on stands to release grey metallic cubes on the other side, where their partner could pick them up to place on more giant buttons and open sealed doors.

After what felt like hours of running and signalling to each other using lasers and hand gestures, they finally raced across adjacent platforms to arrive at the common exit. Panting hard from the exercise, he spotted the familiar particle field through the door leading up to the lift which would take them to the next test chamber.

:: Excellent work. Please proceed to the chamberlock. Mind the gap. ::

"Hi! I'm Jack," the white-haired teen introduced himself cheerfully, transferring his portal gun to his left hand before offering him his right.

"My name's Hiccup," he replied politely after catching his breath, reaching out to shake his hand with a small smile.

Jack grinned at him and let go, stepping back to gesture at the exit. "Come on, partner! Ready for the next test?" he asked, a challenging glint in his eyes.

Hiccup smirked in response and dashed past him without warning, eliciting a surprised "hey!" before he heard excited footsteps chasing him into the lift. The metallic doors sealed shut with a whoosh after Jack tackled him inside, laughing with glee.

Author's Note: Blue is Jack and Green is Hiccup, if you haven't already figured that out. The color of their jumpsuits and portals also correspond to their test subject names. You can assume Hiccup was woken up in the same manner as Jack. I just switched the POV around when it came to the co-op stage here.

Details about the test chambers will tone down significantly from here onwards. If anyone has any comments/suggestions for improvement, I'm all ears :)