Growing up, Mabel and Dipper heard things, things that nobody else heard. They both saw things that nobody else saw. Consistently throughout their childhood, there was an 'imaginary friend', a triangle named Bill.

He was yellow, could fly and was often depicted in their drawings with one eye and a top hat on. This 'cute imaginary friend' had lost its charm once the twins were old enough that imaginary friends should be a thing of the past.

Countless times had Mr and Mrs Pines walked in on their children, talking to an empty spot in the corner of the room, and waiting for its seeming response. Both of the twins seemed to have the ability to see him. To be honest, it first started worrying their parents when the twins both had heard the same response from him. The person, or rather creature, who wasn't actually there. How had they both heard the same response from something that wasn't there?

They could both see him. The could both hear him. They went to a psychologist who simply said that they would grow out of 'seeing their imaginary friend' when they were ready.

Bill eventually wasn't seen anymore. There were no more instances of playing or talking with the imaginary friend anymore. Their parents seemed to be placated by this news, happy with the fact that the unsettling yellow triangle wasn't there anymore. Well this was how it seemed when the twins were awake. The moment they shut their eyes to fall asleep it would be a different story. Bill was there in their dreams, never threatening, but always feeling a little menacing.

Used to his appearance in their lives, they went on normally. Dipper and Mabel learned not to respond to his quiet prompts in their head in front of other people who couldn't see him. It would just protect them from people thinking that they were insane.

Over time, Bill's influence over them became more prominent, and they giggled at things that other adults would find purely horrifying. They cackled loudly in a heart dissection during a sixth-grade science class.

The instructions were ignored, and Mabel had taken extreme pleasure in squeezing excess blood out of it and stabbed her brother in the thigh with a scalpel. His blood started convulsing out of the wound, they both glanced at it and laughed psychotically. They never seemed to feel the pain. Dipper found a strange hilarity that came with pain, no matter if it was his own or somebody else's.

Although they couldn't see Bill during the day anymore, he could still be heard, commenting on everything they did. Influencing many of their choices, like whether or not to have orange juice instead of milk with their breakfast.

Bill delivered on every promise.

The promise that if they wrote down exactly what he said, they'd pass every test. The promise that if they had orange juice instead of water with breakfast, they'd have more energy.

Bill was trusted, they didn't really question him. Bill was more like a parent to them than their actual parents ever were. Their real parents were always running off to work every morning and dumping them with a babysitter. But Bill? He always had time for them.

When they turned ten, Bill started doing Astral Projections of himself again, but this time in a human form. His human form looked like a teenage boy that was lean, nicely tanned and had a trendy fluffy masculine haircut to match his golden locks.

He had an eyepatch over one eye, wore a suit with a pale yellow shirt on underneath with a black bowtie and top hat to match. This time, it wasn't just them that could see him, as long as he had a physical connection to one of the twins, he was anchored into their reality.

He looked like a wealthy teen, that wasn't too bad looking either. He seemed completely normal to Mabel and Dipper. The plus side was that whenever he held Dipper or Mabel's hands, the physical connection allowed other people to see him as well, and their mother swelled in pride that her children had a friend.

The only weird or supernatural thing about him was they could hear him in their minds, and the fact that he had once changed from a triangle to a person, but they just chalked this fact up to their younger childish imagination. Bill, which they had started to call 'Will' ever since he had a human form, was extremely nice. He had even somehow convince their mother that they should get a family pet - a fluffy black kitten with two yellow eyes. All he did was snap his fingers.

—

It was the summer of their twelfth year on the planet when their parents announced that they were going to stay with their Great-Uncle Stan for the Summer in a place called Gravity Falls, in Oregon.

Once they told Will, he was ecstatic, saying that he'd meet them there.

This summer was going to be great.