Character Analysis
In the sixth chapter of The Interpretation of Dreams, Freud tells about a personal dream in which a young acquaintance of his is attacked in writing by the very famous (and very dead) writer Johann Wolfgang von Goethe (6.8.21). Although Freud does not reveal the identity of the young Herr M., he does note that one of the real-life inspirations for the dream was the recent publication of a very critical review of a work by Freud's close friend Wilhelm Fliess (6.4.38).
With this in mind, the "Herr M." who appears in Freud's dream has very little to do with Freud's real-life acquaintance. Instead, his presence serves to conceal the fact that the dream is really about Freud's concern for Fliess.