Iron Man 2 cast keeps growing
The crammed cast of A-list stars already includes Robert Downey Jr, Gwyneth Paltrow, Don Cheadle, Jon Favreau, Mickey Rourke, Sam Rockwell, Samuel L Jackson, Scarlett Johansson, Garry Shandling and John Slattery.
Favreau (Four Christmases) also directs the follow-up to last year's Iron Man, which is co-written by Tropic Thunder's Justin Theroux.
Gregg returns to his role as Agent Coulson who works for the Strategic Homeland Intervention, Enforcement and Logistics Division, aka Shield.
Scrubs star Cheadle will be replacing Terrence Howard (Crash) as Colonel James 'Rhodey' Rhodes in Iron Man 2, which is due out next year.
Kate Mara appeared as Heath Ledger's daughter in Brokeback Mountain and has also appeared in hit TV series 24. Her next film, Flying Lessons, about a girl who returns to the hometown she wanted to forget, is due for release this year.