What’s wrong with your eye!?
An accident had happened, that accident the Pines family as well as Wendy and Soos tried to prevent from escalating.
Their attempts failed, however, Dipper and Mabel Pines had both died trying to help preventing this accident. Bill Cipher, a dream demon, never wanted that to happen.
The Mindscape
So the dream demon performed a type ritual that split his existence into both of the twins, that does mean they acquired the powers Bill had.
”X'M FWTGY V OQI YBC VLO CENAEO QPIO GPKH.”
Bill chanted with his eye closed, his triangular form glowing bright yellow as he performed the ritual even further.
”X HBXG IHVA YXLY UCZE HX HDR ZG OXSGIMTS.”
He kept chanting the chants repeatedly, as he glowed brighter. The ritual was working, and the demon disappeared once it was completed.
In the woods of Gravity Falls
Dipper and Mabel were laying in the grass above a hill, their hands loosely intertwined just like the way they died.
Soon enough, Dipper jolted up from what seemed to be like a slumber to him. He had let out a heavy gasp trying to regain his breathing, he was confused on why he was.. alive?
Then he heard rustling beside him, he glanced at Mabel, who was slowly waking up from whatever nap this was.
“Mabel.. Are you okay?” Dipper asked with concern, his right eye was closed slightly but it would reveal how it was yellow with a cat-like pupil.
“Yeah, I think so…”
“Oh my gosh! Dipper, what’s wrong with your eye!?” Mabel exclaimed in disbelief, as she pointed at his right eye.
“My… eye?” He questioned, he moved a hand up to his eye.
“It kinda looks like..”
“Like Bill’s eye.” Mabel pointed out, Dipper pointed back at Mabel at her right eye that was on his left.
“My eye?! What about YOUR eye?!?” He exclaimed with shock, this was weird.. What was going on?