"Mabel! Are you okay?"
The boy scrambled to his feet, wincing from the scuffs and scrapes he'd gotten from the fall as he parted a nearby patch of flowers to find his sister gazing dazedly up at the sunlight streaming in from the crack they'd slipped through. There was a bruise forming on her chin and her hands were just as scraped as his, but otherwise she appeared to be mostly unharmed. Exhaling a gusty sigh of relief, the boy helped her climb to her feet.
Instead of saying anything immediately the way he'd half-expected she would, she continued to quietly observe their new, strange surroundings, taking in the earthy browns and greens of the moss that grew over damp patches of rock, the alternating reds and oranges in the stone, brought out by the fading rays of a sunset that was quickly working its way below the horizon, before finally settling on the golden petals brushing their legs with a delighted grin. Then she peered over the boy's shoulder, the wonder that had shined so brightly slowly draining from her expression as confusion crept in to take its place. "Dipper," she whispered, "is that flower staring at us?"
He turned sharply to see that a new flower had appeared out of the cavern's floor. It was similar in appearance to the flowers that had broken their fall, the same honey colored petals sprang from its head, but this one had eyes, small and beady. It had a mouth. Noticing him staring, the flower smiled almost shyly, waving a leaf in greeting. A surprised, high pitched squeak forced its way past Dipper's lips as he quickly backed up, keeping his sister behind him.
"Howdy!" the flower cheerfully called. "My name is Flowey. You two must be lost." Its petals drooped with sympathy for the poor hapless human children.
Relieved, Mabel nodded fervently, always eager and ready to make a new friend no matter how strange the circumstances, especially if that new friend was a flower. "Oh my gosh, you're so cute! Can I pet you?"
"Um…" Before the flower could think up a decent response that wouldn't immediately injure the human girl's feelings, she impulsively reached out to stroke one of its petals. A hand clamped around her wrist, not tight enough to hurt through the fabric of her sweater, but enough to momentarily draw her attention. With her bottom lip protruding in the beginnings of a pout, she glanced up to see a fierce, guarded expression on her brother's face. Dipper glared hard at the smiling flower, body language tense and wary. "Don't touch him, Mabel. We've never encountered a talking plant before. For all we know, it could be an evil mastermind or something."
That sounded completely unreasonable. Villains weren't cute, adorable, harmless flowers that popped up and said things like, "Howdy!" And Mabel was just about to tell her brother off for being paranoid when something dark flitted over the flower's face, so fast she could almost convince herself she'd imagined it. Almost.
Sensing her sudden change in attitude, Dipper glanced back at her; curious as to why she wasn't trying to convince him he was acting crazy. "What's wrong with you two?" The flower asked innocently, a trace of hurt mixing in with its usual sickly sweetness. "You're not going to survive long here in the Underground without a friend on your side. Here," floating projectiles bearing the appearance of seeds surrounded the twins, spinning around their heads, circling in closer with each rotation, "take these friendship pellets. They'll help you on your journey."
"No thank you!" Mabel said quickly, ducking her head. "We're good, actually. So if you'll just let us leave- " She broke off with a scream as the pellets violently closed in on the spot where her head would have been had Dipper not suddenly pushed her off her feet. A new volley appeared, faster this time. The twins were forced to roll to escape as it plowed into the ground.
Flowey frowned. "Stop moving, you two. Can't you see I'm just trying to help you?"
"Help us?!" Dipper screamed back, fists balled at his sides as though he'd give anything to wrap his hands around the flower's stem, "You're obviously trying to kill us!"
At his words, the flower changed, transforming into something that bore a better resemblance to a grinning gargoyle with petals than anything that could be described as cute or cuddly. "You've got it! You're smarter than most of the humans that fell down here, I'll give you that." With a nonchalant leaf shrug, he added, "You're still going to die, though."
The last attack was faster than the rest. It surrounded them, blocking any chance of exit. Dipper grabbed Mabel's hand. "We're going to be okay," he said with as much confidence as he could muster, and was rewarded with a watery smile as she squeezed back.
For the first time, Dipper truly understood, all the way down to his core, how love could make a person capable of hate. Because he was going to die and Mabel was going to die and that stupid flower was going to keep smiling and there was nothing he could do to stop it. Nothing. And if they somehow survived to see the next few minutes, nothing was going to stop him from plucking him and yanking every petal off his head.
It wasn't to be, though. Someone intervened.
A small twister, no larger than a dust devil, blew into the room with enough wind speed to sweep Flowey up and carry it off. And, no, small twisters shouldn't occur underground, but that thought was quickly shoved aside and forgotten the moment a goat wearing a dress walked into the room with the posture and dignity of a queen. "Forgive me, my children. Had I known you were in danger, I would have come sooner."
Breaking away from him with a happy squeal, Mabel rushed forward, practically trembling with the suppressed urge to run her fingers through this new creature's fluffy white fur. "You're beautiful," Mabel said sincerely, causing a reddish tinge to color the monster's cheeks.
She laughed. "Why, thank you, little one. It is not very often that I hear such heartfelt compliments. Would you both like to come inside? My home is not far from here, and I am afraid you'll both catch colds if you linger outdoors for much longer."
Dipper bristled at the invitation, still healing from the bleeding, blistering rawness that their first "friend's" betrayal had rubbed at his already limited ability to trust. If it were up to him, it'd just be him and Mabel, but the flower had been right about one thing: If they were going to survive in a world where physics was ignored and animals could talk, then they were going to need friends. Preferably powerful ones. Despite that, he still had to make sure. "How do know we can trust you?" Mabel shot him a dismayed look, deflating, but even if she didn't like it, she understood where he was coming from, and took a step back from the goat woman with an apologetic shrug of her shoulders. "We don't know anything about you."
"My name is Toriel." The goat woman said immediately, a relieved smile erasing some of the distress watching Mabel step away from her had brought. "As long as you are with me, you have my word that no harm will come to you."
Deciding this decision was too important to be left solely up to him, Dipper gestured for Mabel to come into a huddle. While they placed their hands on each other's shoulders, Toriel's long, floppy ears twitched with amusement.
"What do you think? Should we follow her?"
"What's our other option, bro bro? Stay here and wait for the world's meanest weed to come back?" A shiver traveled through her arms, the cavern's draft sinking into the fabric of her sweater, making it heavy and cold. She sneezed.
Biting down on his bottom lip, Dipper glanced at Toriel, who appeared to be struggling against the urge to wrap them up in a blanket and carry them. "You're right. We don't have much of a choice here." They broke up their huddle to face Toriel, their hands still clasped, a ward against the encroaching dark. Dipper raised his head to say clearly, "We've decided we'll go with you… if you'll still take us?"
Without warning, two arms easily wrapped around them both, pressing them against a chest that smelled strongly of cinnamon and butterscotch. The scent felt warm in their noses as Mabel sank into the embrace, tired and hurt and still so trusting, still so willing to believe that Flowey was just a fluke, a bad seed, and they'd be able to make it in this world, to find their way back home. Dipper didn't have her inexhaustible ability to trust or her optimism, but that was okay. Because she did. So he let some of the tension drain from his shoulders, let himself savor a comfort that could end at any second, and promised himself that he would never be caught off guard again.
Ha! That's right, kid! You can't trust anyone down here. Not even the voices inside your head!
Well... that was beyond worrying.
He shifted in Toriel's embrace, pressing the side of his head against the fabric of her clothing so he could see Mabel, only to notice how tired she looked. She was smiling the same way she did after their mom brushed the knots out of her hair before bed, her eyelids drooping, her head hanging heavily as the steady beat of Toriel's heart threatened to send her straight to sleep. Seeing his expression, Mabel forcefully pushed back against her drowsiness, rousing just enough to lift her head and say, "What's wrong, Dipper?"
Smiling weakly, Dipper replied, "It's probably nothing, Mabel. I just need some sleep, that's all."
"I think," Toriel said as she picked them both up, cradling the two of them in the crook of each arm, "it is time for the both of you to get some much needed rest. When you awake, I shall have a wonderful surprise in store for you."
A/N:This is heavily inspired by mudkipful's crossover art on tumblr. I actually finished the first draft of this before seeing more than a few images of their gravity falls/undertale au, so the fact that a certain significant interaction lines up is kind of just a really cool coincidence.