From the Super Mario Wiki
In The Super Mario Bros. Super Show! episode "Love 'Em and Leave 'Em", Queen Rotunda, a long-time admirer of Prince Pompadour, has her servant, Hildy create a Passion Potion, which would make Prince Pompadour fall in love with Queen Rotunda. Unfortunately, due to accident, Queen Rotunda ingest the Passion Potion instead of Prince Pompadour and falls in love with the first person she sees, Mario.
Later in "Love 'Em and Leave 'Em / Will The Real Elvis Please Shut Up!", Prince Pompadour appears as an attendant of Queen Rotunda's forced wedding to Mario. Before he can marry Queen Rotunda though, Mario loudly decides to tie his shoe, distracting everyone present and allowing Luigi to pour some Passion Potion in two nearby glasses.
Seeing that Luigi has poured some Passion Potion into a pair of glasses, Mario hastily grabs them and proposes a toast to Queen Rotunda and Prince Pompadour and gives the two the glasses. Drinking the Passion Potion, Queen Rotunda and Prince Pompadour instantly fall in love with one another.
Completely love-struck, Prince Pompadour asks Queen Rotunda to marry him, which Queen Rotunda agrees to. Hearing this, Prince Pompadour instantly embraces Queen Rotunda.