I have recently found mention of Lorenzo the Magnificent in three books I was reading. In one (by Elizabeth Peters) one of the characters was a fan of his, in another (Tey's Daughter of Time) someone thought a portrait of Richard III looked like a portrait of Lorenzo, and then he was mentioned in a third book.

In all three cases I got the impression there was some joke involved, but I didn't get it. Can anyone explain this to me?