Scarlett Johansson is reportedly attached to the third installment of the Iron Man franchise.According to Latino Review, a casting call for the movie lists Johansson as a confirmed cast member as her character Black Widow/Natasha Romanoff, who was an assistant to Tony Stark (Robert Downey Jr) in Iron Man 2.Johansson, who will be portraying Black Widow in the upcoming Avengers film, previously said that she would like to see a "gritty” movie about the comic book heroine."I love playing the Widow,” she shared. "I think she’s got a very interesting past, a lot of storylines to explore, and certainly [producer] Kevin [Feige] loves that character.”The Avengers will open to cinemas on April 26 in the UK and May 4 in the US, while Iron Man 3 is set for a May 3, 2013 release.