The Royal Order of the Holy Mackerel is a secret society. It is mentioned in Rumble's Revenge in a cryptogram that says, "There is a secret society in Gravity Falls." Stan is probably a member, because a cryptogram in Made Me Realize says, "Stan is not what he seems." Soos may be a member too, due to another cryptogram in Rumble's Revenge saying, "The handyman knows more than you think." Bill may also be involved.