Jackie Coogan was amazing, I really loved Michael Chaplin in A King in New York. Mack Swain in The Gold Rush was adorable (he was in some Chaplin shorts as well, but best in Gold Rush). Sydney Chaplin in Limelight was lovely.
Coming out of left field, I’m going with Oliver Johnston from A King in New York. He played Ambassador Jaume, and was a great straight man to Chaplin’s King Shadov. Both of their reactions to American culture (wide screen movies, rock and roll, TV commercials, plastic surgery) as well as the growing paranoia that was McCarthyism was very funny. I have watched the film several times, and it never disappoints. Partly due to their onscreen camaraderie. Also Michael :).
It would have been interesting if Chaplin had been able to use him in any of his earlier films.
Johnston’s last film appearance was in Chaplin’s A Countess From Hong Kong, which was released shortly after he passed away.