You become a real person from the moment you are born. Some would say from the moment you are conceived.
Mermaids are not real. They do not exist and are from stories. A person can not become a mermaid.
Make a video about yourself and show you the real person and you will become famous. 
In real life, there are no such things as were-cats. So it is impossible.
Show me the money first........
It is about what it means to become a well-balanced person and a real man.
the REAL person to discover Americas mothers middle name was America
can vampires become real
No, fictional characters can not become real.
All 3 creatures you ask about are not real and you can not become any one of them. Be happy as a person.
All the property, real and personal, that a person owned at the time of their death will become part of their estate.
Fairies like "Tinker Bell" are part of "fairy stories". Fairy Stories are fictional creations and the characters are not real. Therefore I am sorry to say that "Fairies" are not real, they are imaginary beings and it is impossible for a real person to become one.
There are no spells or anything else that can turn a person into a mermaid. Spells are not real. Mermaids are not real and these things only exist in films and movies.