Ford Pines

The Author of Journal 1, 2 and 3 is the long-lost brother of Stan Pines, who has spent several years investigating the supernatural side of Gravity Falls, Oregon, before his eventual disappearance into the Universe portal. He was assumed deceased until he was found alive during "Not What He Seems."

Early Life
In the 1970s, the Author settled in Gravity Falls in the midst of his travels, dedicating six long years to studying the supernatural secrets of Gravity Falls. His discoveries were recorded in a series of journals encrypted with a polydactyl hand, representing his own hand possessing a sixth finger. Recruiting the help of a local technician, Fiddleford McGucket, the Author's work centered on drafting plans to build a machine capable of benefitting all mankind. However, as construction went on, McGucket grew fearful of its inevitable failure and the destruction it would inflict, quitting the project and erasing all memory of it. Desperate to finish his creation and confident in its ability, the Author carried on the crafting of the device.

At one point in his stay within the town, the man summoned and befriended Bill Cipher, deceived by the demon's seemingly affable nature. He soon saw through the facade and sought a way to defeat him, and was seemingly successful. As his work in Gravity Falls continued, the Author found himself increasingly paranoid and fearful, developing a fear of an unknown entity referred to only as "He." Now writing in his journals via invisible ink, the researcher took extreme security measures in the creation of an underground laboratory serving as a fallout shelter, keeping it hidden beneath the Gravity Falls forest. To take further methods of ensuring his work's safety, the Author hid his three journals across the town, intending to keep their knowledge separated. In 1982, in the midst of documenting Journal 3, the Author vanished into the Universe portal, however he reappeared from the portal, during the events of "Not What He Seems."

Following his disappearance, Journal 1 fell into the hands of Stan Pines, who began a search for his journals as a means for the Author's machine to function, spending 30 long years hunting for their knowledge. He remained among one of the few people aware of the journals' power, the other being Gideon Gleeful, who was able to locate Journal 2.

Season 1
In "Tourist Trapped," Dipper unwittingly stumbles upon his third journal and becomes entranced by the information it contains, and he quickly begins to use this knowledge to aid him in his encounters with the supernatural. By "Scary-oke," the boy's investigations eventually lead him to seek out the Author, convinced that finding him will be the key to unlocking the greatest secrets of Gravity Falls.

Eventually, Dipper and his family become entangled in Gideon's quest to learn the Author's secrets, convinced this knowledge would give him unprecedented power that would allow him to take over Gravity Falls. Gideon nearly achieves his goal of gaining all three journals in "Gideon Rises," but is stopped by Dipper and Mabel. His defeat enables Stan to seize possession of Journal #2, and Dipper's revelation of his ownership of Journal #3 lets him complete this same goal.

Season 2
After learning about the invisible ink in his Journal, Dipper leads his friends into the Author's bunker to search for clues on his whereabouts in "Into the Bunker." There, they come face-to-face with the mysterious figure's 210th experiment, the Shape Shifter. After successfully recapturing the beast, they emerge with their greatest lead yet: the Author's laptop.

In "Sock Opera," Dipper devotes himself almost excessively to cracking the password for the laptop. After innumerable failed attempts, he makes a deal with Bill Cipher, but is tricked into letting the demon take possession of his body. Bill destroys the laptop to prevent Dipper from coming any closer to finding out some "major answers" and attempts to do the same to Journal #3, but is stopped by Mabel.

In "Society of the Blind Eye," after discovering that the laptop was manufactured by McGucket Labs, Dipper becomes convinced that Old Man McGucket is the Author of the books. In his confrontation with the elderly man, Dipper learns of the mysterious Blind Eye Society and goes to look for them. Recovering McGucket's stolen memories from the society reminds him that he worked side by side with the Author, and begins trying to remember the man's identity.

In "Not What He Seems," it is revealed that Stan has been collecting radioactive waste, for the purpose of powering a doomsday device, and the twins encounter an old newspaper article which claims Stan Pines to be deceased. Contrary to this incriminating article, it is discovered that Stan Pines is at least the direct brother of, if not, the one mentioned in the article who is actually alive. At the same time as this discovery the author of the journals is definitively identified, after his emergence from a portal in the center of the afore mentioned 'doomsday device,' by Grunkle Stan's reference to him as his "brother."

Appearance
Being the twin of Stan Pines, The Author resembles him greatly, there are, however, a few notable differences. He appears younger than his brother, still having brown hair which is only partly grey. He also doesn't have a stubble like Stan does, only a few hairs on his chin. He is seen wearing a large black coat with multiple pockets on the inside, and an item that appears to be a gun rested on his back. Underneath his coat, he wears a black shirt and pants. He also dons bulky black boots, a brown belt that slings from his shoulder, a tattered cape, and a gray scarf. He is a polydactyl (meaning he has an extra finger), and, in fact, has six fingers on not just his left hand, but, it appears, on his right, as he displays when opening his coat at the end of "Not What He Seems". It also appears he is Ambidextrous (able to use both hands for things like writing), as he picked the journal up and put it in his coat with his left hand, but when he is writing ideas for possible hiding places he is using his right hand

Quotes
"It's hard to believe it's been six years since I began studying the strange and wondrous secrets of Gravity Falls, Oregon."

- In Tourist Trapped.

"Unfortunately, my suspicions have been confirmed. I'm being watched. I must hide this book before he finds it. Remember: in Gravity Falls there is no one you can trust."

- In Tourist Trapped.

""When fighting the Gremloblin, use water... only as a last resort as water will make him much much scarier!" AH! Who writes sentences like that!?"

- Dipper Pines reading one of the Author's pages in Boss Mabel.

"If my suspicions are correct, this is the work of Fiddleford. Does he really have to go to such great lengths to forget?"

- In Society of the Blind Eye.

"The portal when completed will open a gateway to infinite new worlds and herald a new era in mankind's understanding of the universe. Plus, it will probably get girls to start talking to me finally."

- In Gideon Rises

Trivia

 * Alex Hirsch has on multiple occasions joked about the Author's identity:
 * He "leaked" a false image of a younger Old Man McGucket writing in a journal.
 * Via his Reddit AMA and Twitter account, he has stated the Author is actually Geordi La Forge from Star Trek: The Next Generation.
 * The main aspects of the character bear similarity to Abdul "The Mad Arab" Alhazred of Lovecraftian lore. Like the Author, Abdul Alhazred wrote a cryptic book about monsters and magic (The Necronomicon) and disappeared without a trace after completing this work, which he went to great lengths to hide.
 * He is mentioned in Season 1 and Season 2 until making his first actual appearance in "Not What He Seems."
 * Assuming that he's not Dipper and Mabel's grandfather, it can be implied that Stan and the Author must have at least one other brother who is the father of Dipper and Mabel's father.
 * In Journal 2 on Bill Cipher's page, there's a quote saying "He's in my wallet!". Under it, it shows half of the back of a -12 dollar bill. This is odd, considering Quentin Trembley's time in office was long before the Author was born. This may mean that the Author is a collector.