Reversion Spell

The Reversion Spell is a magic spell that Gargamel used on Smurfette in order to change her back into her unsmurfy self.

Smurfs (TV series)
The spell appears in the cartoon show episode "Smurfette Unmade", which is used by Gargamel after Scruple suggests changing her back to her old self.

Due to the spell only appearing once, only one ingredient is known which is a pinch of pesky powder, and an incantation muct be said, which is: The time is right, the spell is set, now give me back my old Smurfette.

Hero: The Guardian Smurf stories
The spell first appears in the story "The Dark Hero", which only reveals the ingredient: a pinch of pesky powder. It was used by Gargamel to originally change Smurfette back to her old self, but instead Hero took the full force of spell and became an evil being. The spell wore off when Gargamel planned of using Wonder for the gold-making formula.

The spell appears again in the story "One's True Origins", used by Gargamel II to change Smurfette back into her evil self, but instead changes her daughter Miracle into an evil Smurf. The story reveals all the ingredients needed for the formula, which include:
 * a pinch of pesky powder
 * a viper's tongue
 * 6 dragon scales
 * 8 bees wings
 * a crocodile tear
 * a trolls toe
 * blue clay