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, adapting to whatever continuum in which the badfic is set.
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. Aura of Smooth can also be used intentionally by rubbing it into the skin like a cosmetic product. Overdose by a normal character can lead to Suedom.
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.
Aura of Smooth is a Class A Forbidden Substance at the International Academy of Hetalia Fanfiction. A nurse there was once convicted of possession and using it to destroy security. She was deported to PPC HQ for de-glitterification.