icauser, may I just ask for clarification of your queries?
You say " a book's title character" - meaning presumably a fictional character whose name (or a short description) is present in the title of the work in which the character appears?
Such as the example you gave "Harry Potter and …..."
But Atticus Finch for example does not appear in the title "To Kill a Mocking Bird"...…….
Could we please have more guidance here?