Did Ken Curtis star in any John Wayne movies?

Yes, Ken Curtis starred in several John Wayne movies. He is most known for his role as Festus in the television series "Gunsmoke", but he also played supporting roles in a number of Wayne's films, including:

* The Comancheros (1961): He played the role of "The Kid"

* The Man Who Shot Liberty Valance (1962): He played "The Bartender"

* McLintock! (1963): He played "Crazy"

* The Sons of Katie Elder (1965): He played "Dave"

He also appeared in the John Wayne-produced film The Alamo (1960).