When the Martin Kellum character comes up to Doc's office, in which they reveal that the two have known each other from the past, Martin calls Doc by his first name, Galen, six years before a previously mentioned trivia fact that states he was allowed to choose his first name. This is also confirmed in closed captioning of that episode.
Roger Ewing plays one of the Luken boys in this show. Next season, Ewing will join the regular cast as Thad Greenwood.
Galen was a common nickname for doctors after the American Civil War. It let the doctor know you are also educated. It was considerably more favorable than sawbones, and not as formal as doctor or doc.
The sign above the undertaker's establishment reads "Elias Foley", instead Percy Crump, the usual undertaker.