"Don't tell me what to do!" Cries out the stereotypical teenager at his parents.
"You dumb fuck!" says his father "You just told ME what to do, You fucking hypocrite!"
Runs after him with a blade and cuts him up to little pieces.
Arrr! Murder, yeah!
This phrase is tagged to the end of one's speech in order to reveal an innuendo or undertone. It is expressed with a wide-eyed expression and a tone of confusion. It is often synonymous with "That's what she said".
Unlike "That's what she said", it is proper for one to add this phrase to the end of his/her own speech, as well as for others to do the honor for him/her.
Scott: "This female's pelvishas been articulated... I don't even know what that means"
You know the expression "the left hand doesn't know what the right hand is doing"? Meaning, usually, two arms of a larger entity (two departments of a major corporation, for example) aren't communicating well.
"The left hand doesn't know what the left hand is doing" means that things are so completely fucked up that they don't even know what they themselves are doing.
I can't get my healthcare provider to acknowledge that I've already paid them using the debit card issued by the very same healthcare provider. The left hand doesn't know what the left hand is doing.