I originally read this as suggesting that The Cyberiad was inspired by GEB; but, of course, chronologically, it could only be the other way.

Not that I doubt you, but do you know any reference for Lem's fondness for GEB?

In "Thus Spoke Lem" - a several hundred pages interview with Lem - there is a chapter about Lem's likes and dislikes in literature. He is asked about books which influenced his thought and he mentions several of them, read when he was young. When asked about later influences he talks about GEB and Mind's I only. He says that again and again he sees in those books concepts similar to his own, but he is sure that Hofstadter reached them independently. I do not think that an English translation of Thus Spoke Lem exists.

Another connection between Hofstadter and Lem: in Le Ton Beau de Marot there is a chapter where Hofstadter discusses possible ways of translating How the World Was Saved from Cyberiad.

I'd never heard of that interview; now I'll have to see if I can find a copy. Thanks!