Underfalls: A Gravity Falls/ Undertale Crossover

❤Chapter 1- Welcome To The Underground!❤

Ok hey everyone a few things before we start:

I do not own Gravity Falls, or Undertale or any characters or plots of either series, Undertale belongs to Toby Fox, and Gravity Falls belongs to Disney©. I only own my fanfiction, and nothing else.

I can make spelling errors from time to time so don't criticize me if i get something wrong.

Finally, i hope you enjoy this story! This is my space-book im writing to back off of scenarios and let the people decide the next step. Plus, i need to write a crossover. Ive never done a Gravity Falls, or Undertale crossovers, so ive deicded to do this one! Hooray!

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DipperPOV

I blinked open my eyes to find myself  laying on a patch of yellow wildflowers, none that I've ever seen before. My sister, Mabel, was already bouncing around like nothing was wrong. Heh... Thats typical Mabel. I picked up my cap that was lying on the flower bed, and adjusted it back on my head, then closed my eyes as i tried to remember what had just happened. Then the memories came flooding back.

~~~Flashback~~~

My Great Uncle Ford had returned to our realm not long ago. As we talked, we became more friendly with one another, and soon, i discovered that i wasn't the first fool to fall for Bill's trickery.

Bill is a inter-dimensional.... Well... We aren't really sure what he is, but he is planning to cross over into our world, and everything we know about it.

"Dipper, there is one last thing to prevent Bill's reign of terror for good. You must climb to Mt. Ebbot, not far from here, and retrieve some inter-dimensional travel-block. It will prevent Bill from ever crossing into our realm, and taking over our world."

"Ok Great Uncle Ford. I'm on it-"

"Oh and Dipper?"

"Yes Great Uncle Ford?"

"Take Mabel with you. Its dangerous to climb Mt. Ebott one. Legends say that those who climb the mountain never return. Be careful Dipper,"

"I will. Thanks Great Uncle Ford..."

~~~Timeskip brought to you by Ducktective~~~

We were just climbing and climbing, and then i hear Mabel scream. Her foot had caught  on a vine, and i had grabbed her hand at the last moment. But i was loosing my grip too. I just knew one thing: failure. Then everything went black...

Now we were here, in... I'm not sure where, but its a place I've never seen before. I let Mabel dash around the flower bed, straying farther and farther from me, until she became a bright, pink dot in the dark and desolate caverns. Then, i hear her shout, echoing throughout the caverns, and finally reaching to me. "Hey Dipper! Check this out!"

I get up, stretching the stiffness in my limbs away, and I start to walk a steady pace towards my sister, my footsteps echoing in the deep cave. Her image slowly became bigger and bigger, until I had reached her, and i saw that she was pointing to a large door, closed, but by the looks of it, unlocked.

"Should we go in?"
"Well, you are the smart one. You decide." Hesitantly, i reached to touch the door, and to my suprise, it opened pretty easily. Our footsteps echoed as we walked into the next room, to find another patch of flowers, one in particular smiling widely at us. It was weird. Was i hallucinating? I was about to pinch myself when it spoke to us.

"Howdy! I'm Flowey! Flowey the Flower!"
"Hi I'm Mabel, and this is my brother Dipper!"
"You're new to the Underground, aren't cha?"
"The Underground?"
"You don't know about the Underground? Well, it looks like little ol me will have to do!"

Flowey winks, and instantly, a screen appeared before us, a crimson red heart planted directly in the middle.

"See that heart? That's your SOUL, the very culmination of your being! Your SOUL starts aout weak, but it can grow stronger when it gains just the right amount of LV! What's LV stand for? Why, LOVE, of course! You want some LOVE, don't you?" Mabel nodded eagarly as i just sat there in silence. "Don't worry! I'll share some with you!"

Flowey winked again, sticking his tongue out this time, and little, white objects that looked like shards of glass surrounded the flower's head. "LOVE is shared through... Little, white... 'Friendliness Pellets.' Are you ready? Get ready! Move around and collect the pellets!" As if an instinct, Mabel started to head for the bullets, but at the last moment, i sensed that they werent safe, and i made the SOUL dodge at the last moment. "Dipper! What are you doing?"

"For some reason, i don't trust him. Not one bit."
"But hes going to help us! Why wouldn't you trust him?"
"Yes. Let your sister make the right desicion." Sighing, i put my hands up and backed away as Flowey summoned more pellets, and let Mabel run into them. Then i felt a sudden pain in my chest, and i cringed. I managed to look up to see Mabel was on her hands and knees, in excruciating pain- and then i looked at Flowey.

A devilish grin was spread across the flower's face, and he started to growl. "You idiot. In this world, its KILL or BE KILLED. Why would ANYONE pass up an opportunity like this?" a circle of more bullets surrounded our SOUL, and he growled "DIE," before allowing the bullets to close in. I gripped my chest in not only pain, but fear as well. "Mabel..." i murmered as i squeezed my eyes tight, gritting my teeth. But i blinked open my eyes when the pain was suddenly relieved, and the sound of fire wooshed not far from me.

Flowey was gone, but instead, a kind, she-goat stood before us, and held a hand out to help me up.