Penelope Cruz's actress sister was used as a body double for the star in some scenes in the latest Pirates Of The Caribbean film.
Penelope, who was pregnant with her son by her actor partner Javier Bardem during the making of the film, was replaced by Monica Cruz during filming in London.
Rob Marshall, director of Pirates Of The Caribbean: On Stranger Tides, said: "We actually asked Monica to help us out with some of the wide shots and some of the long shots when we needed a different silhouette."
He told a press conference at the Cannes Film Festival Monica was "fantastic and a real friend to the film".
Penelope admitted she struggled with the physical demands of her role as a swashbuckling female pirate opposite Johnny Depp but said the toughest challenge was "to keep a straight face in front of Johnny, that was really difficult".
The film is about the search for the fountain of youth, but the glamorous Penelope said she was not worried by the prospect of growing old.
She said: "Birthdays are something to celebrate, I'm looking forward to every step of the way.
"Maybe because I'm from Spain that's looked at in a different way there than for example in a place like Los Angeles or in our industry but I will always be a Spanish actress working there wherever I go to and there are a lot of things I keep from my roots and that's one of them, the way we look at that.
"I never want to be afraid of that, change is good."