User blog comment:ThePK/The Official Boss Mabel Speculation/@comment-4784313-20121106005430

Heres my idea:

Stan left Mabel in charge for a day because something happens with Soos and Wendy. While he's gone, Mabel feels the true power of the Mystery Shack come to her. Will Dipper find a way to stop whatever will probably happen to Mabel if she does find the true power? Stay tuned!