Board Thread:General Discussion/@comment-5094906-20131019134332/@comment-908565-20131128041406

We do know for sure. Not only is there the Genie's reference in "Fruit of the Poisonous Tree" to how Regina "could have chosen any snake in the world" but chose one from his homeland, implying that it's all one world, the episode "Ariel" makes it definite because Eric is going to travel "the desert from here to Agrabah".