Other mistake: At the beginning when Festus rides up and finds Riley Sharp handcuffed to the hitching rail, if you notice the handcuff chain is draped over the top of the hitching rail and there is nothing preventing him from sliding the chain off the end of the railing.
Gunsmoke (1955)
1 mistake in The Intruder
Starring: James Arness, Ken Curtis, Amanda Blake, Milburn Stone
Dr. Galen 'Doc' Adams: I'll tell you why the Hagens live so long.
Festus Haggen: Why?
Dr. Galen 'Doc' Adams: 'Cause they're too dumb to know they're dead.
Trivia: Although they played father and son in this episode, Jack Elam was only six years older than Harry Dean Stanton.