Colin Firth has a cameo appearance in one of the Bridget Jones novels.
That’s the first one I thought of- and small wonder J.D. Salinger was outraged.
Think of all the psychopaths who are devoted to*** Catcher in the Rye***, and who think Salinger is the one person who understands them!
Salinger was already living in seclusion, partly because he was afraid of the kinds of people who were obsessed with him. Now, imagine that one of these crazies started “hearing voices” telling him to kidnap Salinger!
Can you see why he was less than thrilled with that plotline? And why, at his insistence, he was replaced in the movie by a fictitious author played by James Earl Jones?
Ursula Andress, who played Honey Ryder in the James Bond film Dr. No, shows up in Fleming’s On Her Majesty’s Secret Service. She’s described as having a fresh tan, as you’d expect if she had been filming in Jamaica before going to ski in the Alps.
Similarly, in one of John Gardner’s James Bond novels he mentions Bond watching an in-flight movie about Prohibition agents that starred a Scottish actor that he particularly liked. But he gave no names.
IIRC, in Whitley Streiber and James Kunetka’s War Day, the authors are the main characters and they visit fellow writers Chelsea Quinn Yarbro and Walter Tevis (who was alive at the time).
Asimov is yet another author who’s written himself into one of his own books (Murder at the ABA). And Heinlein included thinly-veiled pastiches of himself and other SF authors at the end of The Number of the Beast.
I have an uncle who’s the chief of a suburban police force, and got a cameo (with the author’s permission) in a murder mystery set there.
As the pattern indicates that living people appear in novels only if they’re too famous to notice as with Presidents and such, are friends of the authors, or the authors themselves, it’s simple to assume that there are legal ramifications for depicting a living person in a fictional context. Any lawyers here who can confirm?