Make a portal, go to the nether, freak out and come back trough same portal. Appear somewhere else.
Go back in the nether, mess around and fall into lava.
Respawn, get more obsidian and go back in the nether. Walk a bit and make a portal within the nether.
Use the portal, come out outside near a hill. Climb the hill, look around, realize I am not in the same save file anymore.
My face --> O_O
Mind is blown. Is that a bug or is it intended?