Board Thread:News and Announcements/@comment-14298735-20130803020216/@comment-17456017-20130903001354

My guess is Stan. During the theme song, Stan is shown with an eyepatch, therefore he has a "blind eye", as people with eyepatches have lost an eye or something. Also, it shows that Stan knows something about Gravity Falls, as he has all 3 books and built a device and combined all the books (shown at the end).