@SeraphimDawn
Griffonstone was implied on the official out-of-show map, albeit not by name. Last time I checked, the
only location implied that was visited later was that bear’s cave first mentioned in Party of One that later appeared in Too Many Pinkie Pies.
The only one. Unless you decide to include Manehattan on a technicality, though IIRC it was first mentioned in The Cutie Mark Chronicles