It might not be unhealthy, if its making you happy. It would be considered unhealthy in the sense that you might no longer know what is reality, which could mean that you have a form of schizophrenia which is a result of an enlargement of the butterfly in your brain (Aka the butterfly effect). But even then, health wise, you might be just fine.
I have, but it was more out of boredom than anything else. I find it kind of fun to come up with scenarios to see if I'd be compatible with a certain type of personality.
In some instances, I could say it's unhealthy, though.