The gang accept Jonathan Winters' invitation to stay at Maude Frickert's farm, to take a break from chasing ghosts. But little do they realize that there's a phantom scarecrow running around the Frickert's farm.
When the gang first see Jonathan Winters at the gas station, he acts as an attendant and asks "What can I do for you?" With the Mystery Machine short on gas, Fred tells him to "Fill 'er up", but his lips don't move as he speaks.
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What happened to all of the chickens?
During the scene in which one of the chickens, which looks more like a rooster to me, eats the Frickert formula, he grows in size while the other chickens, Scooby, and Shaggy look on in amazement. When he gets so big that he makes the walls around the chicken coop collapse, you only see Shaggy, Scooby, and the overgrown chicken, but not the other chickens. In fact, they are never seen again.
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Shaggy: My fellow Americans...let me make one thing perfectly clear... (popular phrase used regularly by Richard M. Nixon, President of the United States at the time)
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