Plot hole: Wouldn't the other secret societies be expecting the Skulls to try to steal their mascot? After all, they claim they have stolen every one but the one they steal in the movie. So that one must know they are next. Yet these Skull wannabes all very noisily and clumsily manage to get the weathervane without any problem. It is hard to believe a secret society would be so easily robbed, especially if they had SOME inclination that the attempt would be made.
Plot hole: A true secret society of that calibre would never allow itself to be known to the point that a perspective pledge would know the deadline for when his last chance would be to become a member.