This does not seem to be a widely known folktale, but it does appear in a volume (which can be purchased here) edited by Toshio Ozawa, a reputable Japanese folklorist. You can hear him tell the tale in Japanese on his radio program online.
Once upon a time there lived a man named Chōkichi. He was so given to telling tall tales, that the village people called him horafuki Chōkichi (something like “great storyteller (a.k.a. mostly liar) Chōkichi”).
One day, a wealthy man called out to Chōkichi.
“Chōkichi! I heard you are a great horafuki. Tell me a story!”
Chōkichi replied, “It doesn’t matter how skilled I am, I can’t tell you a good story on such short notice.”
The wealthy man replied, “Oh, I see. In that case, come to my house tomorrow. I will fill a tray with gold coins. If you can make me say, ‘That’s a lie!,’ I will give you the gold coins. But if you cannot make me say ‘That’s a lie!,’ you must work for me for free for one year.”
Chōkichi agreed and went to the man’s house the following morning. As promised, there was a large tray of gold coins at the house. The man welcomed Chōkichi.
“It is fine weather today,” said Chōkichi.
“Indeed it is,” said the man.
“After I met with you yesterday, I had business in town.”
“Oh? And how was that?”
“I saw a lord riding a horse and his procession of servants.”
“How did they seem?”
“There were many servants carrying a great, heavy box. It was quite a sight!”
“That sounds like a lord.”
“But just then, bird poop fell from the sky and landed on the lord’s shoes.”
“And what happened?”
“His retainer intoned loudly, ‘A chaange for my looord’s shoes!’
And straightaway, a good set of shoes was brought out and exchanged.
But again bird poop fell from the sky and landed on the lord’s coat.
“His retainer intoned again, ‘A chaange for my looord’s coat!’
And straightaway, a good coat was brought out and exchanged.”
“That is something.”
“But, at that point, again bird poop fell from the sky and landed on the lord’s forehead.”
“His retainer intoned loudly, ‘A chaange for my loord’s head!’
And straightaway, a new head was brought out and exchanged.”
“Chōkichi! That’s a lie!”
Chōkichi immediately said, “And now I’ll have those gold coins.”