Some major Summer blockbusters have been adding new faces to their cast over the course of the past week.

Though the casting of Chris Evans in the role of Steve Rogers in Joe Johnston‘s The First Avenger: Captain America and the news that Joss Whedon would be directing The Avengers has without doubt stolen the spotlight, there was still work to be done.

Hayley Atwell, who has starred in films like The Duchess and the TV mini-series remake of The Prisoner, has now been cast as the Captain America female lead, Peggy Carter. Atwell will be playing the the love interest of Rogers, and her character could become much larger depending upon how they take her comic book storyline and transfer it to the screen. Many actresses were looked at for this role, including Keira Knightley and Emily Blunt.

The First Avenger also stars Sebastian Stan as Bucky Barnes and Hugo Weaving as Red Skull. It will be released on July 22, 2011.

Pirates of the Caribbean: On Stranger Tides has also been at work adding some new talents to their film.

Sam Claflin and Astrid Bergès-Frisbey have both been cast in the fourth Pirates film, which will open a couple of months prior to Captain America on May 20, 2011. Clafin will be playing some type of young missionary (milkshake?), and Bergès-Frisbey will play the “key role” of Syrena, who is said to be a “beautiful and alluring” mermaid.

So long as Ariel doesn’t show up, this mermaid deal should be interesting to see. All of these actors are still in the youngest stages of their careers, so in a little over a year we should have a much better idea of what they bring to the party.

[Sources: Collider, Heat Vision]