How much can you squeeze out of a comedic premise, particularly the mistaken-identity trope that was already collecting dust by the time "Petticoat Junction" got hold of it?
This gentle, innocent situation comedy was determined to find out with "Is There a Doctor in the Roundhouse?" which finds Norman Curtis (Roy Roberts), the "hobo" freeloading at Kate Bradley's Shady Rest Hotel who is actually the president of the C & FW Railroad--and who was trying to mothball the Hooterville Cannonball until he found out how much fun it was to drive it himself--still hanging around Hooterville Valley, to the chagrin of Uncle Joe Carson.
In fact, Norman was having so much fun that he broke the throttle on the Cannonball trying to show off going up Bleeker's Hill, as Charley Pratt and Floyd Smoot report back at the Shady Rest, which is preparing for the valley's jamboree, now threatened with cancelation since, with the Cannonball the only viable way to get to the hotel, no one will be able to get there. And with the steam-powered locomotive a museum piece already--they stopped making that kind of throttle a half-century earlier--it seems unlikely that the Cannonball can be repaired.
So, was this deliberate sabotage on Norman's part? He says he was trying to arrange having a flatcar attached to the Cannonball to bring even more guest to the jamboree--but can you really trust these city slickers, anyway? Particularly those looking to shut down the train service in the first place?
There's the situation in this episode of your situation comedy, with Ed James and Seaman Jacobs's script plumbing it for all it's worth. Norman sincerely wants to remedy the situation and, relying on his connections to the old-boy networks, calls in some high-powered, albeit now-retired, talent to help him repair the Cannonball, but when they arrive in grubby clothes to start the dirty work, they're mistaken for Norman's fellow hobos instead of the former captains of industry (and one former Air Force general) they really are.
To provide context for contemporary viewers, when "Petticoat Junction" first aired, the Great Depression of the 1930s was still a vivid event for older viewers drawn to the show and its suggestions of bygone days. (And likely for younger viewers with better historical memories than we have now.) Men, particularly older men, fallen on hard economic times often "rode the rails" (stowed away on trains without paying) and congregated in "hobo jungles" often located near railroad tracks. Older viewers who were movie fans quite likely got a kick out of seeing Norman's pals played by long-time character actors Douglass Dumbrille, Charles Meredith, and Addison Richards.
Roberts, an industry veteran himself, is the star of "Is There a Doctor in the Roundhouse?" which finds ample opportunity for the denizens of Hooterville Valley, particularly stubborn Uncle Joe, to doubt his Norman as he tries to prove who he really is as this dusted-off premise, already familiar to viewers at the time, plays out in predictably comforting fashion.