The cowboy who tries to stab the Duke in the barfight is Chuck Roberson. Roberson was a stunt man/actor with credits in over 20 John Wayne films.
John Wayne previously guest-starred as himself on "I Love Lucy" and the episode title was also called "Lucy and John Wayne".
Hanging on the wall in the studio commissary, is a photo of Bob Crane from Hogan's Heroes.
Lucy mentions to John Wayne that Maureen O'Hara is usually in his pictures. Lucille Ball and Maureen O'Hara starred together in Dance, Girl Dance (1940).
John Wayne would also go on to guest star on "The Lucy Show" in an episode also titled "Lucy and John Wayne"