The actors play retired secret agents in the action film, alongside Morgan Freeman and John Malkovich, and at one point in the picture, The Queen star is seen holding a large firearm.
Willis admits he swooned when he saw his ""sexy"" co-star posing with the weapon, and told producers he would quit if they dared to remove the scene from the final edit.
He tells Fox News, ""I said if that scene is not in the film I want them to take every shot of me out of the movie. But it's in. It's so... it's just sexy. Who knew? I think Helen would've been doing action films a while ago - with that .50 calibre machine gun in a ball gown. Wow!""
Willis wasn't the only one impressed by Mirren's action skills - Malkovich adds: ""What more could you want than Helen Mirren with a firearm? One can pass over to the other side and be happy.""