Once you get past the stereotypes these actors were locked into by the script writers, they're still damn good actors. Here's the pressbook for Charlie Chan and the Feathered Serpent. Mantan Moreland expertly provided the comic relief for many movies, including King of the Zombies. Playing the servant role at a time when Hollywood accepted such limitations for audience consumption, he transcended his chauffeur and butler characters to make otherwise lacklustre movies worth seeing just for him alone. He became a key draw for the Charlie Chan series from Monogram. At one point, Moe and Shemp Howard seriously considered him for a role as one of the Three Stooges. He was that good.
Comic Book Reader Version: Download Charlie Chan Feathered Serpent Pressbook