Go West, Young Monkey - S5.E15

The Doorman orders a western town for his train set and Steve, Betsy, and George offer to help him put it together while he's at work. Hundley supervises. When the group accidentally sends a small pin from the train track into one of the plant pots, they must dump out all of the soil to search for the missing piece. Hundley falls asleep and dreams of himself and the group in a real western town. In his dream, George finds out how to make proper sifters to efficiently search for small objects, but in the end Hundley's sneezing is the secret to finding the pin. Reference: spaghetti western.