When you're dealing with the older ages - someone in their 50s, say, and then someone in their 70s - it's just a lot harder to find two actors who are similar. When you get into younger people - the teenager to someone in their 30s obviously, people can change a lot in that time.

We try to match some facial features. We bring [the people] in. They don't have to just look alike, but have to have the same energy, to seem similar.

You'll always want to find an actor in the larger role first.