Daniel Craig
Daniel Craig plays a private detective named Benoit Blanc. Rian Johnson sent Craig the script for Knives Out but he couldn't star in it because of his next James Bond movie, No Time to Die. Johnson's first choice for the role was Craig, so he was disappointed that he would have to find someone else for one of the most important roles in the film. After No Time to Die was postponed, however, Craig was able to star - which he eagerly did.
After doing extensive research, Craig decided to base his speech pattern on a historian named Shelby Foote, who he thought had an interesting accent and manner of speech.
Ana de Armas
Ana de Armas plays the nurse and is named Marta. In October 2019 Ana de Armas joined the cast after reading and liking script. De Armas says that she was interested in the role because it was one of the few lead roles in holly wood that was written specifically from someone from her background. "I was blown away [by the script]," de Armas said and "fell in love with the character." "Marta," she said, " is something I've never seen."