"Your mouth is writing checks your ass can't cash," is something TV Dr. Phil McGraw's father said to him as a boy when he would voice wild plans or notions. It means that talk is cheap relative to performance, or that promising something and delivering on it are two different things. A phrase similar in meaning is "Money talks, bullshit walks."
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"I'm going to get a job selling fuzzy dice door-to-door. I'll be rich!"
"Boy, your mouth is writing checks your ass can't cash."
This is a phrase one would use to proclaim that someone's posterior can produce one of 3 things, A. a loud and boisterous fart, B. a long winded and detailed fart, or C. a fart that produces a particularly foul odor when leaving someone's shitter. Almost always used after someone farts, and it is not courteous to proclaim that someone's ass, can indeed, fart, outside of a scenario in which said person previously farted in the last 15 seconds. You may also add 'though' to the end of the phrase if it suits your fancy.
*Someone in closevicinity starts ripping some serious ass.* "That ass can fart!" or "That ass can fart though!"
State in the United States of America otherwise known as Kansas. Known for its extreme religiosity, intolerance of gays, and political conservatism (excepting of course the massive farm subsidies given to the state by Uncle Sam).
Dorothycame from Can's Ass, but unlike her I am glad to be out of that barren cultural wasteland and cesspool.