What is the point of World Order, and why do certain characters seemingly have the freedom to just travel wherever/whenever they want?
The villains make sense, as they use Corridors of Darkness to bypass the Lanes Between, but what about Santa? He has a list that includes Sora and Riku from an entirely different world. Merlin also just gets away with straight up teleportation from Hollow Bastion to Disney Castle.
Then you have instances that are left ambiguous, like Monster's Inc. Are the doors just different locations in the "Monster's" Earth, or are they doors to other worlds entirely? I would think the former, but chucking Vanitas through one seemed to work instead of him just... teleporting back. The latter would explain why he didn't return again for a while. But then how did Monster's Inc. discover the secrets of inter-world travel?