Craig in 'Craig It's Kind of a Funny Story' remains a mystery. He could be a relatable character that the author uses to tell a story that is both funny and meaningful. Maybe he has some quirks or habits that make him stand out and drive the humorous plot. It could be that as the story progresses, we learn more about Craig's background, dreams, and what makes him tick.
I don't have enough information to say exactly who Craig Rosenberg is in this context. He could be an ordinary person whose life has been made into a story, or perhaps he is a public figure in a particular community and his story is being told.
Billy Elliot is based on a true story to a certain extent. It incorporates real elements but may have fictionalized parts to enhance the drama and entertainment value.