A significant amount of history predates the events recounted in Fraggle Rock. These historical periods are often only mentioned in passing, but are occasionally seen through flashbacks or (in one case) time travel. Events in Fraggle and Doozer history can only be dated relative to one another. For instance, no Doozer constructions are visible in the episode "Mokey, Then and Now," suggesting that the Doozers had not yet left the Cavern of Lost Dreams.