The famed parody of Asimov and Heinlein. Amongst other issues, the book asks what happens to all the garbage from a one city planet (a la Trantor from FOUNDATION)? It seems to be a losing battle down below, but the planet's topologists have come up with an empty soda can that spontaneously deforms into a long playing record, which the user naturally wants to keep.

I'm not sure, but I have the impression that Harrison once read the joke about a topologist being a mathematician who cannot the difference between a coffee cup and a doughnut, but completely missed the topological point of the joke.