From the Super Mario Wiki
In the episode, the gluttonous Queen Rotunda has her servant, Hildy, create a large batch of Passion Potion for her; Queen Rotunda wishes to use the Passion Potion on Prince Pompadour, wanting to make him fall in love with her. Unfortunately, the Passion Potion is ingested by Queen Rotunda herself, causing her to fall in love with the first person she sees, Mario.
Later on, Queen Rotunda, during her forced wedding to Mario, ingests another dose of Passion Potion, as does Prince Pompadour, who happens to be nearby. This results in the two falling in love with one another and subsequently marrying; unfortunately, Hildy also drinks some Passion Potion accidentally dropped into the wedding punch bowl by Luigi and ends up falling in love with him. She then chases him, Mario, Princess Toadstool and Toad across Rotunda Land.
Mentioned ingredients of the Passion Potion include one spring mistletoe, one ripe artichoke heart, and one Fat Boys record. Creating a Passion Potion seems to be somewhat difficult, as when Princess Toadstool and Toad attempt to create some, the potion explodes violently.