Ghostwriter is a children's mystery television series created by Liz Nealon and produced by Children's Television Workshop (now known as Sesame Workshop) and BBC Television.
The series revolves around a multiethnic group of friends from Brooklyn who solve neighborhood crimes and mysteries as a team of youth detectives with the help of a ghost named Ghostwriter. Ghostwriter can communicate with children only by manipulating whatever text and letters he can find and using them to form words and sentences.
I know I watched a lot of this as a kid, but I don't remember any of it except for some cool effects with text spelling out something. That part was always exciting.