Goblin Gold

 a limited-time currency that was released on October 3, 2017 for Act 1 of the Treehouse of Horror XXVIII Event. It the only currency used to craft prizes for the event.

They can be obtained:
 * By tapping Goblins that spawn in the player's town.
 * By tapping Goblins in the player's neighbors town.
 * From personal prizes.
 * (TBA)