The `Pirates of the Caribbean: On Stranger Tides` actress - who has a five-month-old son, Leo, with husband Javier Bardem - insists she isn`t vain about her appearance and is happy to change her looks to suit her characters.
She said: "I`m not scared to be ugly when I work - so I often ask for more moustache or black bags under my eyes."
The Spanish beauty also revealed she prefers to be asked to change her accent for her movie roles because she becomes less critical of herself and more open to experimenting with her characters.
She explained to Closer magazine: "I love to spend hours with the dialogue coach because it creates a distance from myself. That way I don`t hear Penelope talking - I don`t criticise myself so much and have more freedom to try things.
"My grandmother was very gypsy in her spirit and she taught me to love words, especially poetry and flamenco and music and drama."