'Morris' columns, or advertising columns, have been part of Parisian street furniture for a hundred and fifty years. In 2006 the mayor of Paris, Bertrand Delanoe, started to implement a campaign to reduce the number of these columns in an attempt to 'declutter' the streets. The move was protested as an attack on the arts, as theatres and galleries still use the columns to promote their shows.
There is an urban legend that the columns contain spiral staircases leading down to a network of secret catacombs. Unfortunately, the prosaic truth is that they usually contain equipment for the Parisian street cleaners.
The Testaments de César Girodot is a 1876 three-act comedy by Adolphe Belot. Oedipus Rex, the Greek tragedy by Sophocles, is the basis of Freud's theory of the Oedipus complex. It is the second mention of an incestuous text in Swann's Way (see also the bookmark for p. 47, "she had chosen François le Champi").
The Diamants de la Couronne (The Crown Diamonds) and the Domino Noir (the Black Domino) are comic operas by Daniel Auber.
Got, Delaunay, and Thiron, Febvre and Coquelin are all real French actors from the turn of the century. The only fictional one is Berma, who comes after Sarah Bernhardt in the narrator's reckoning. Berma is the first of Proust's four archetypal artists to appear in the novel.