People who create a person in their minds that are tangible and real to them are clinically called schizophrenics. This is not true for all people. Small children are known to create a person that grown ups call their "imaginary friend". Creation of an imaginary friend does not necessarily mean the child has a disorder. Pretend friends can actually be beneficial in a child's development.
. Imaginary friends tend to show up in children between the ages of two to six. This is an age where reality and fantasy quite distinguished in a child's mind. You can find more information here: http://parenting.ivillage.com/tp/tpbehavior/0,,7mdx,00.html
