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 pelvis has been articulated... I don't even know what that means"