“The Long Walk” isn’t like most movies. When a group of 50 young men from the nation embark on a cross-country contest to see who can walk the longest without stopping, they quickly become a unit.

For a series like The Pitt, casting can be an incredibly time consuming and involved process. With over 300 roles to fill, casting directors Cathy Sandrich Gelfond and Erica Berger need to comb ...