Frog Magic is a type of wand magic related to frogs. It is a reference to the LeFrog family curse.
This magic can turn anyone, the user included, into a frog. The spell will last until the cursed one receives a kiss. Just like the original curse, a kiss will restore them to their true form. All objects and clothing disappear when they are transformed and reappear when restored.
Frog magic cannot change someone if they are under a stronger curse. In "The Grand Ball" Joy could not change the donkeys into frogs as Candlewick's magic was stronger than hers. Someone with the ability to shapeshift at will can also break the curse.