When it was first seen, SAD was being kept in a large metallic vat hooked up to several tubes and a prominent nuclear symbol on it. After the vat holding the refined SAD was split open by Law, the substance is revealed to be somewhat of a foamy mixture similar to wax.
SAD is a particularly unique substance and it is one of the few things needed to create SMILEs, which are artificial Zoan Devil Fruits. Caesar Clown created it via the practical application of Vegapunk's and Vinsmoke Judge's discovery of the universal genetic blueprint: the Lineage Factor. The substance itself is a mix of Lineage Factors from a wide variety of animals, and when the SAD is transmitted into fruits to create SMILEs, the Lineage Factor is intended to alter the user's body and give them the characteristics of a specific type of animal.
According to Shinobu, the SAD formula is still incomplete. Thus, the SMILE fruits it produced have an extremely high risk factor; only a 10% chance of success in granting artificial Zoan-like enhancements to consumers, with a 90% majority not getting any powers and only suffering the side effects. While successful SMILE's mimic a real Devil Fruit's weakness of taking away the eater's ability to swim, the duds, in addition to taking away the eater's ability to swim, have an added side effect of taking away the eater's ability to express negative emotions, causing them to constantly smile and laugh, regardless of how they actually feel.
Caesar is the only person in the world who knows how to manufacture SAD. As such, SAD is very valuable, so much so that Donquixote Doflamingo instantly figured out Law's intentions regarding the SAD storage room, being aware that its destruction would have been disastrous to his underworld empire.
It has the potential to cause anarchy within the New World, depending on the one who wields it. It also might have some radioactive properties, as the symbol for radioactive substances appeared on the tank Law was looking at; and Law himself noted that the laboratory will soon explode after the state he left the SAD production room in.
Punk Hazard Arc
Trafalgar Law apparently went through great lengths to gain access to the SAD production room on Punk Hazard, joining the Seven Warlords of the Sea and then forming an alliance with the Straw Hat Pirates. He eventually succeeded amidst the chaos in the research facility, but Vergo contacted Doflamingo and reported it. Vergo was ordered to stop Law from taking the SAD and execute him for his betrayal, which leads to the two of them battling in the production room.
Despite the destruction of the production facility in Punk Hazard and Caesar's captivity, the Donquixote Pirates still possessed a decent quantity of SAD in their factory, as the dwarves continued their labor of cultivating SMILEs. Ultimately, the remaining SAD supply, along with the SMILE Factory, were all destroyed when the dwarves rose up in revolt.
- SAD is similar to the Joker Venom from DC Comics, as both were created by someone with the moniker of "Joker" (Joker and Doflamingo) and cause a permanent grin with its victims.