What if you entered through a portal to this hell world, but instead of it being a completely different world with a hell binome, it would be a copy of the normal world but everything is the opposite.
Except for around the portal all grass would become fire on dirt.
Water into lava.
Trees leaves fall off and catch on fire.
Pigs, Chickens, sheep and Cows stay as the same model (angry face maybe?) but attack you. I'm thinking sheep could exploded creeper style, Chickens shoot you with feathered arrows.
All the zombies, creepers and skeletons would become nice? maybe try and protect you from the evil cute creatures until they are turned into cute creatures themselves.
Just an idea I was playing with.
note: I do not expect any or all of this to be taken seriously nor do I expect or demand Notch to do any or all of this. This was simply an idea I had