The following takes place in an alternate version of Gravity Falls where Grunkle Stan didn't have a twin brother who wrote the journals, however the journals where written, just not by Stanford Pines. In fact Grunkle Stan's real name was actually Stanford Pines, and he wasn't trying to activate the portal to save the author. All will be explained in the following written below which takes place at the end of the episode "Gideon Rises" where Stan is reacting to Dipper is telling him about the third journal; though some scenes will be taken from the "A Tale of Two Stans" episode.
Birth of the Mystery Shack (Alternate Version)
I can't believe it, thought Stanford Pines. His nephew Dipper had just revealed that he'd been in possession of a book that apparently, was the reason why Gideon had tried to take over the Shack in the first place, (well besides trying to get revenge on his family just because Mabel wouldn't be his girlfriend). It shocked him because he never thought he'd ever see the book after giving up the searching for it ten years ago; yet here it was, in his hands.
"Grunkle Stan," Stan turned his head around to see Mabel, (his niece and Dipper's twin sister), looking at him curiously.
"Is everything okay," she asked.
"Ya Grunkle Stan," responded Dipper who also appeared curious to his uncle's behavior toward the journal. "You blanked out for a few minutes. Do you know something about this journal and why Gideon wanted it so badly?"
Signing to himself, Stan realized that he needed to tell them the truth; after all they had a right to know.
"Ya kid I do know what this is. It's one out of three journals written by a mysterious scientist who wrote these other two as well." As Stan said this he pulled out the first two journals from inside his coat.
Dipper and Mabel gasped in shock, their eyes bulging up like balloons. While his sister was just in complete shock with no idea of what to think, Dipper had so many questions including what in Gravity Falls was happening? Where did his Grunkle Stan get the first journal? How he'd get the second from Gideon? (Though he figured his uncle had stolen it from him when he reclaimed the deed to the shack when Gideon was arrested) Had he known all this time about the super naturals of this town? What other secrets had he been hiding? This and many other questions fill the young boys mind as he tried to figure out which to start with.
"Gru Gru Grunkle Stan?" was all he could say.
"Kids I can explain," the old man replied suspecting what was going on inside his nephew's head.
TO BE CONTINUED…..
This was originally supposed to be a one shot, but this is my first fanfiction on this site and decided to post this part and finish it off later.