From Original Star Trek, I have one favorite episode called "Parallel Universe" where mirror image of existing universe present. My favorite character Spock, who is emotion controlled half alien is very emotionally violent in another universe. I love this episode since it deals with fantasy that in other universe we might be something very different.
But if you look carefully in our world, every entity itself is Universe be it material, plants, animals. It carries complete history from it's origin. e.g. Sample of rock can tell what geographical changes happened from its time of creation to today. Same is true with DNA of animals.
In human world, we have evolutionary path similar which described above. But socio/economic front, we all live in parallel Universe. Take example of any person - his nature, family background, social strata, his mental block.. which create itself universe. We see some orthodox families, once we enter in their house we feel like entering into 16th century feudal's home. At the same time we find some indigenous people living in woods. On other hand we see some technological geek using all latest technological gadgets and wandering future course of humanity. How does nature manage to keep this diverse Universe on one planet?
These are extreme cases which are not majority. What about majority people like us?
We do live into our own Universe, but there are many Universe .. be it family, society. As far as these Universe are parallel there is not much problem but once it start colliding, friction happens and we loose our own tiny Universe and thrown into some unknown parallel Universe.