Jeez, has everyone been on this show? For this list, we’re looking at celebrities who appeared on “ER” in small or minor roles - so no mains or leads like good ol’ Clooney - before getting their big break and becoming household names. Our list includes Jessica Chastain, Zac Efron, Eva Mendes, Nick Offerman, and more! Join MsMojo as we count down our picks for the Top 10 Stars Who Appeared on ER Before They Were Famous.