Washington, Pattinson, and Debicki were cast in March 2019. Each of them were only permitted to read the screenplay while locked in a room. Nolan chose Washington based on his performance in BlacKkKlansman (2018). Washington kept diaries in which he expanded the Protagonist's backstory. Pattinson took some of Neil's mannerisms from political journalist and author Christopher Hitchens. Kat was originally going to be an older woman, but Debicki's appearance in Widows (2018) convinced the filmmakers otherwise.