The best short films are Deconstructing Sally, The Heirs and Karaoke Tonite!
What we have here, in essence, is the "star" equivalent of the film student's low budget movie. Many of the same constraints and story strategies apply. The entire story has one central location, the house where the anniversary party takes place. The story is character-driven, an ensemble piece. There are no special effects and less visual storytelling than is common in a Hollywood movie. The film, in fact, definitely has a "stage play" feel to it.
The Anniversary Party is a play-like, character-driven ensemble story -- with Hollywood stars in all the roles! Only digital technology makes this adventure possible, and it will be interesting to see what other stars use the revolution to make the journey from actor to writer/director.
It also will be interesting to see how this movie and others like it do with audiences. If they do well, then it's a point for the kind of character-driven, slowly developing story that in the past has been the mainstay of theater but difficult to market to Hollywood. In other words, new story strategy options are being offered to mainstream audiences now, and if the audiences react positively, this might permanently affect the way stories are told in Hollywood.