Opposite world is a world in which everything is opposite to the world we live in today. For example, In opposite world salt is pepper and pepper is salt. There are several theories and conjectures about opposite world, outlined below.
The logical theory of opposite world
Contention # 1: In opposite world, everything is exactly the same as it is in this world. Salt is pepper and pepper is salt, but in opposite world salt tastes and looks like pepper and pepper tastes and looks like salt, so they are effectively the same thing. Salt (now pepper) would be black and vice versa. It takes no more than 2 changes to make an object exactly the same.
Contention # 2: In opposite world, it is possible to change two objects around, but not their relationship to other objects. For Example: Say for argument that in this world women spent time at the sink, while men spend time at the TV. In opposite world women are men and vice versa, so women would spend all their time watching TV while men would be at the sink doing the dishes. But the TV is the Sink in opposite world, so everything would be back to normal. However, if we try to change the relationship around as well by saying "in opposite world women spend time watching TV while men spend their time at the sink", contention # 1 would fall down.
Contention # 3: You must "oppositize" all features and properties of an object at the same time, and you may only oppositize them once. Changing the colour, but not the smell of a rose will make it something that is NOT the opposite of a rose. If you then change the features separately it's possible to make more than two changes to objects, thus making them not exactly the same as they are in this world. Unfortunately, this seems to be at odds with the example in contention # 1, which changes the name of the salt separately to its properties. We may allow this - I'm not sure.
Case Examples for the logical theory of opposite world
Opposite Shaft Opposite shaft would be white. But in opposite world black is white, so that's the same. His face would be on the back of his head. But in opposite world back is front, so that's the same. He would walk backwards. But in opposite world forwards is backwards. Opposite shaft would have no beard, but in opposite world a clean shaven face has lots of hair.
The "Pure" theory of opposite world
Contention # 1: Everything in opposite world is opposite - including relationships to other objects. It is not possible to imagine what opposite world is like, or to define rules for it until you have "oppositized" everything and drawn all possible conclusions. Only then can you say whether it is the same, and how many times something has to change around.
Contention # 2: In pure opposite world, an oppositized object has a "re-birth" of sorts. It bears no relation to the original object it is, and therefore nothing in pure opposite world can be compared to our world.
Case examples for pure opposite world
Opposite shaft has no beard. In opposite world, having a beard means you're soft, not hard. But opposite shaft is soft, unlike he is in this world. So opposite shaft is hard (because he has no beard) but he's soft as well (because that's the opposite of hard). But having a beard means you have no beard, which means he's hard overall. This case example shows just how much depth pure opposite world can reach.
Bizarro World is different to opposite world in that some objects are oppositized (or even changed to something random) while other objects remain the same. Thus the objects which have been changed are bizarre. For Example, Elvis could be alive in bizarro world, but he is still dead in opposite world. Hell, Elvis could be a jelly baby in bizarro world.