Pushing "Stan"ity | Gravity Falls AU | Canon X OC

Prologue: The Spider Demon's Arrival

  Ford was working in his lab, just have gotten done with a game of Dungeons, Dungeons, and More Dungeons with Dipper when a bright purple light appeared in the lab. Ford was confused, his glasses barely working as a protector from the blinding light. A spider looking creature emerged from the light. It was a grayish purple, but still purple. He got up from his desk and grabbed the nearest weapon, which just so happened to be a wrench, and pointed it at the demon, "Who are you and what do you want from me? We're you sent by Bill?"
The demon looked confused, "Bill? As in, Bill Cipher? No. I haven't talked to the triangular moron in years." Ford realized it had a really feminine voice, "Are you a girl?" He asked, his wrench going down lightly, "Yes. I'm a girl. Sorry. You must not be able to tell in this form of mine?"
Confused by what the demon was saying, Ford was taken aback from the sudden shift in forms. The spider demon took the form of what he guessed to be a five eleven woman with nearly jet black hair and that same pale purple in her eyes and outfit. Ford was surprised by how she was just nonchalant about showing him her human look, "See, woman, breasts." She motioned to her more feminine features.
Ford just looked away until he heard her hands clasp together, "Anyways! My name is Marvolous, yes, it's pronounced 'marvelous'." His brain couldn't wrap around that. And he had twelve PHDs. She chuckled, "You're Stanford Pines, right?" Her hand was outstretched to him. No mystical fire, just her gloved hand. He shook it, carefully taking his hand back.
"So you weren't sent by Bill?" He asked carefully, "Nope!" Her enthusiasm spoke a lot. She had never been to this dimension has she? Apparently not.
  She floated around the small cramped lab just looking at things, tapping things carefully. Ford didn't know what to make of it, he was so concerned that she could cause a problem for him.. but she didn't seem keen on doing so. Ford turned back to his work and let the Dream demon float and mess with whatever she pleased.
  "That's wrong." She called over his shoulder, looking at the math equation he was working on, "How? I'm sure it's right." Ford looked at her shocked slightly at how close Marvolous actually was. Her eyes flit from him to the paper, "Your supposed to carry the 'y' here." She pointed to where the 'y' was on his paper, "And that comes out to -25." Marvolous pointed to the expression on the paper. Ford looked at her like she just spoke another language, then looked at his paper and reworked it.
  And that damn dream demon was right. It was what she said. Shocked, Ford pushed back from his desk. Hearing a thump come from behind him. Concerned something of value fell, he turned around. Apparently Marvolous was knocked out of the air by him. He made a small concerned face to her and helped the tall one up. That's when Ford realized that her legs were slight gradients. From a normal skin tone to a darker grayish purple.
  He bit his lip in confusion, which got a giggle from the one who's now floating, "Yes, I can explain what my body is. And yes, you can see my entire body naked for scientific purposes." She said with a smile. Ford just smiled back, "Thank you."

  And so he did, Marvolous was sitting nude, well besides the fact all the normal human female parts that had nerves that weren't the mounds on her chest had been removed. Ford analyzed Marvolous carefully, genuinely intrigued. He noticed scars on her back, "What.. if you don't mind me asking, are these scars from?" Ford asked as he rubbed his hand over them lightly, "Oh their from when Bill murdered and destroyed our entire dimension. He wasn't always a sadistic triangle. He used to be a kind young man.. but he got tired of how we were treated. Our parents were dead, our older siblings didn't want anything to do with us, and we were homeless. He had a job, scrounged up enough money for us to live.. but it wasn't enough. He seeked power. Power that could destroy us. And he found it, I was found by it when I was about to die from starvation.."
  Ford took it all in. His kind reeling, Bill wasn't evil before? Why? Marvolous was so eager to tell him anything, he found it suspicious. Yet he didn't say much about it. He just kept studying her, "Hey For-" Stan came out of the elevator. Saw the scene, noticed how Marvolous wasn't human, and the left. He was deeply disturbed by the fact there was a naked human dream demon in his brother's lab.
  "Guess we're pushing his 'Stan'-ity." Marvolous said as she snapped her clothes back on. Ford had gotten enough data anyways.