Marvel Studios works extremely hard to keep its castings and plots secret, but most tend to inevitably leak.

Somehow that wasn't the case with Julie Delpy's casting in "Avengers: Age of Ultron." Her role in the movie was unknown until a tip sheet for the "Avengers" sequel world premiere on April 13 was released.

The Oscar-nominated actress finally spilled what role she will play, and it sounds like she'll be sharing her scenes with Scarlett Johansson's Natasha Romanov, a.ka. Black Widow.

Delpy will play one of the trainers from the Black Widow project, which molded Natasha Romanov into the highly skilled agent and fighter she is today, according to ComicBook.com.

The "Before Sunrise" actress wanted to do a big Hollywood blockbuster, despite being well known for her independent and art films. She said she's not opposed to the big franchise films, unlike some other "art house" actors and filmmakers.

Linda Cardellini also joined as the latest announced cast member in "Age of Ultron." The "Mad Men" actress' role is still unknown.

"Avengers: Age of Ultron" will premiere on May 1.