Aura of Smooth is the field that Mary Sues, Gary Stus, and self-inserts generate that makes canon characters bend to their will. This field may be pheromonal or energy-based in nature, possibly dependent on the continuum in which the Stu is found.
Aura of Smooth is known to be transferable, if temporarily, by ingesting parts of a former Sue—such as a cut of meat, or even Sue blood if large enough amounts come into contact with the bloodstream—without "stripping" the Aura first.
When found in Water, Aura of Smooth lowers inhibitions and/or gives the person who consumed it greater willpower than normal. Presumably, anyway. Just be careful with it.