The cast of 'Mission: Impossible - Dead Reckoning Part One' reveal just how close to impossible the film's stunt work really was. Pom Klementieff (Paris) ran on top of a moving train for the movie, while Hayley Atwell (Grace) had to hang from that same train after the whole locomotive goes off the tracks. Simon Pegg (Benji) admits that watching Tom Cruise (Ethan Hunt) jump a motorcycle off a mountain was absolutely terrifying, and writer/director Christopher McQuarrie divulges that every single stunt was an unbelievable feat of filmmaking for him. Then, Vanessa Kirby (The White Widow), Shea Whigham (Jasper Briggs), and Greg Tarzan Davis (Degas) join in to brainstorm their dream stunt for Tom Cruise to pull off as Ethan Hunt.