Alright, now that I thought abuot this idea, I'm dead set on it. I vote the author is Soos.
I think he wrote it, possibly with McGucket's help, and then either is playing dumb or had an experiment that made him dumb-down (either by accident or on purpose).
Evidence:
1) He's always "discovering" the hidden rooms in the Shack
2) His password fixinit1 (Soos and the Real Girl) fits the number of spaces for the password for the laptop (Sock Opera). [One theory: he "fixed" the laptop with a program to make it shut down...]
3) In the first episode, Stan said "I'd fire all of you if I could." We all know that he can't fire Dipper and Mabel, but what about Soos and Wendy? Also, in the first episode, Soos said "my wisdom is both a blessing and a curse." In addition, he believed Dipper almost immediately about supernatural stuff happening, but told Dipper he needed evidence before making such claims.
Thoughts?