"Oh, that's easy," replied the Pinhead. "You see, after the object is made, we look at it under our big magnifying glass. This magnifying glass is no ordinary magnifying glass, but has the ability to magnify things permanently. It was given to our ancestors by a male witch who had no further use for it."
"Why don't you look at each other's heads with it?" asked the Scarecrow seriously. "Then you'd all have bigger heads."
"Oh, it won't work on living things," replied the Pinhead. "Besides, we like the way we look. How would it be if everyone in Oz looked the same? All skinny or all fat, all tall or all short, all white or all yellow, all blue or all green, all —"
"All right, all right! You've made your point," said the Scarecrow. "My brain is fairly new and it's just not used to thinking that much yet."
"I agree with you, Mr. Pinhead," said Dorothy. The world would be a very dull place if everyone looked the same. Imagine what it would be like if everyone looked exactly alike, thought exactly alike, and talked exactly alike! There would be no point to existence."
"My sentiments entirely!" said the Pinhead.
"Getting back to the business at hand," said Dorothy. "I'm still mystified as to how you create a river to order?"
"Well," answered the Pinhead. "It's quite simple, really. We have this huge reservoir that was created by building a dam to capture the tears of a giant that was a bit of a cry-baby, to say the least. The slightest little hurt would set him off on a crying spell. We turned his excessive crying into a cottage industry by utilizing the stored up tears for our new company, Rivers on Demand, Inc., and since the tears have magical qualities we can direct the river to and fro', uphill or downhill, exactly as we wish to suit the customer's order. The river even knows to avoid dwelling places and other inhabited areas, and to return immediately to the reservoir when its passengers have disembarked."
"Remarkable!" replied Dorothy. "Just remarkable."
With that, they all went down to the newly created river to board the raft that had just been completed for them. After stepping aboard they barely had time to wave goodbye to their new friends as the river quickly whisked them on their way.