The Diary of a Young Girl
Peter in the play
Unlike Peter in the book, Peter in the play starts off being almost mean to Anne. He starts being very pouty about being stuck in the attic. Also, Peter is portrayed in the play as more standoffish than shy, as he is shown in the book. Lastly, Peter in the play starts liking Anne very suddenly in the play, whereas in the book it is a very slow progression.
Both Peter in the play and Peter in the book end up liking Anne. They also both start sort of isolated and distant from the other people living in the attic. A third similarity between Peter in the play and Peter in the book is that they both feel embarrassed about Mr. and Mrs. Van Daan.
Peter in the book
Peter in the play starts off as a shy, quiet boy, unlike how he seems in the beginning of the play. Peter starts out very shy and separated from everyone else in the attic. In the book, Peter starts liking Anne very slowly, whereas in the play it happens very quickly.
Anne's pivotal action
In both the play and the movie, Anne and Peter grow very close. This pivotal action changes Anne's perspective on her situation in the attic. Before becoming such good friends with Peter, Anne was very sad and constantly felt alone. Opening up to Peter helped her feel like she wasn't so alone, and it gave her someone to lean on. She grew so close to Peter because she felt the need to reach out to someone, and Peter happened to be one of the people stuck in the attic with her. I think that without Peter, Anne would have continued to be depressed until they were discovered.