gimtree

A silly story that is untrue but superficially plausible. Usually short, but can go on as long as the recipient is willing to listen. Named after the classical example:

Yeah, I saw a gimtree once.

A gimtree?

Yeah. You know the drink called a gimlet? It was originally with the gim, the fruit of the gimtree. They had special juicers to extract the juice to use in this drink. But as the drink got more popular, they started running out of fruit, so bartenders substituted lime juice.

Really?

Sure. The problem was the gimtree only grew on this one island, and it's not very big. Besides, less than half the island is used for growing gimtrees.

What abou the rest?

They grow cork trees. You know, cork, that stuff they make bulletin boards out of, and of course corks for wine bottles? It's the heartwood of the cork tree. Nice and light, but waterproof, and soft enough you can cut it into whatever shape you need. If they switched over to growing gimtrees on that side of the island, the price of cork would go up, and that would never do. Besides, the gim needs a rainy environment, which you find on the east side of the island, while the cork needs a dryer, sandier soil, which is on the west side. The big mountain in the middle makes a rain shadow on the west side.

(And on and on until the listener realizes his leg is being pulled.)