Board Thread:News and Announcements/@comment-14352346-20130803155903/@comment-25104149-20140523205339

My theory: I think the portal's to protect the world from Bill, in case he breaks out into the world. If he ever doesm terrible things could happen to Gravity Falls, and he will unleash the Time Baby upon the world, which will cause a horrible future, and there will be several agents dedicated to time-travleing to prevent this horrible future from occuring in the first place. When Bill broke out into the world the last time, he took Stan's secret twin Stanley with him.