Before the formal "pene" label became widespread, Castillo appeared in Brown Emmanuelle , a film that helped launch the career of her contemporary, Sarsi Emmanuelle. Directed by Celso Ad. Castillo, the film is part of the local softcore wave that drew inspiration from the Emmanuelle franchise. Myrna Castillo co-starred alongside fellow Softdrink Beauties Pepsi Paloma and Sarsi Emmanuelle herself, marking an early collaboration between these notable stars of the era.
Myrna Castillo's impact on Philippine cinema extends beyond her on-screen performances. Her work, particularly in the controversial 'pene' genre, was a product of its time, reflecting the industry's bold evolution during the 1980s.
During the 1980s, several films featuring Myrna Castillo gained attention for their production styles and the way they addressed social realities. These films are often studied for their contribution to the evolving landscape of Philippine cinema: