Character Analysis
We're not talking wax figures here, although we might as well be.
Norma Desmond regularly meets with a group of three other famous silent-screen stars to play bridge. None of these people have speaking roles, but they actually were famous silent-screen stars in real life (just as Gloria Swanson, who plays Norma Desmond, was). The three faded celebrities, all playing themselves, are H.B. Warner, Anna Q. Nilsson, and Buster Keaton (a master of slapstick).
Obviously, the fact that they're playing a bunch of washed-up has-beens is meant to be a sly, self-deprecating joke on their part. Plus, it heightens the eerie and unnerving true-to-life feel of the movie.