I would choose the movie "Titanic" and rewrite the ending to give it a happier outcome. In the new ending, both Jack and Rose would be rescued together by a passing ship after the Titanic sinks. They would go on to live long, happy lives together, cherishing the memories of their time on the Titanic but ultimately making it safely back to land. This way, the heartbreaking tragedy of the original ending would be replaced with a more uplifting and hopeful conclusion for the beloved characters.