"Ghost Boy" is a look alike version of Timmy Turner.
He is a fanmade character and a look alike version of Timmy. When he came to Dimmsdale he went to Timmy's house he caused a lot of trouble and Timmy wished for a vacum to make him disapear and never come back. Then he returned to go inside Mark's spirit and caused him to be evil.
Ghost Boy has the same style as Timmy except he has green bodie, no hat and ghost hair.