The Carnival - S1-E3
Factual error: After John-Boy reads the scary bedtime story to Jim-Bob and Elizabeth, when Elizabeth is lying in bed she's holding her Raggedy Ann doll, and in the closeup we can see the doll's Knickerbocker tag. This episode takes place in 1933 (the Chicago World's Fair is mentioned at the end), and the Knickerbocker Toy Company created this doll in the late 1960s. (00:09:30)
The Carnival - S1-E3
Continuity mistake: When Esther breaks her eyeglasses, in the closeup as John-Boy picks it up half of its right lens is gone, but in the wideshot as he hands the glasses to Olivia that lens is still intact. (00:03:20)
The Carnival - S1-E3
Continuity mistake: While John and Zeb are making the train arrangements with Sam, just as Zeb calls Homer an old priss Sam opens the clock dial's top hinged glass door in the wideshot, but in his next closeup that door is suddenly shut and it's the pendulum's bottom glass door which is now wide open. (00:29:55)
The Carnival - S1-E3
Revealing mistake: When Jonboy, Jason, Ben, and Elizabeth are trying to lure the monkey down from the tree, the leash it's tethered to is visible down the tree trunk. But then disappears after the monkey climbs down.
The Carnival - S1-E3
Visible crew/equipment: Near the end, when the clowns are performing their act for the Waltons, the monkey's leash is visible as it makes it way across the tightrope, before jumping down.