Can a person have two completely different characters?

I think that is referred to something as " the alter ego" ?? I am a Christian and there is a belief that what can be going on is that there is actually demon performing its game on the person. It's the same for people with multiple personality disorders or schizophrenia. Many people don't believe this, but I do and there has been cases described in the Bible that would fit the picture. In these cases it was indeed demon or a certain amount of demons possessing the body and mind of a person, who after the casting the demons out usually couldn't remember anything of what he/she has done and were very distressed and confused. If it's something that is bothering you, and you are a believer I suggest you'll pray about it to God through the name of Jesus Christ. Whether you are a believer or not, in any case it can be dangerous to nourish or develop this relationship with that other " person". I am not sure if I helped, I am sure people who don't have faith will just classify it as a mental disorder, which can also be the case as demons may not be behind every single diagnosis.