Ben Affleck and George Clooney are two of the biggest actors in Hollywood, who share some close mutual acting friends — and yet they've never shared the big screen.On Sunday, the two movie stars walked the red carpet outside the DGA Theater Complex at the Los Angeles premiere of — which Clooney directed and Affleck stars in -- and they opened up to ET's Kevin Frazier about whether or not they'll ever actually share the screen.«We had great experience working together previously, he produced