Shit Whistler

A Shit Whistler is a person who tell complicated and incredulous lies that they alone believe. The act of doing so is referred to as "playing the shit whistle".

John's a real shit whistler...Last night he told us about how he crawled out on the wing of a flying airplane to fix the engine.

Shit Whistle

I'm not quite sure of it's origin but the first time I heard it was on active duty with the US Air Force some time in the late 1970s.
A shit whistle is the item used by people, known as shit-whistlers, who tells a complicated and evolving tale that they alone believe. In psychiatry the closest term is a confabulation.

"Hey, you should have been at the NCO club last night! John was blowing the shit whistle again..it was a classic!"