The title refers to the production number given by RKO to Citzen Kane.
The size of the principal actors had to be modified for their roles. The 6'3" Liev Schreiber had to bulk up to portray Orson Welles, while John Malkovich, who stands about 6'1" (a full head taller than the real Herman Mankiewicz), had to be made to look much slighter and smaller than usual. James Cromwell, who stands a towering 6'7", was surrounded by actors in lifts, as the real William Randolph Hearst was about 6'3" or 6'4".
In the shot of Orson cutting the Citizen Kane script, one of Kane's lines is "Who knows what lurks in the hearts of evil men? The Shadow knows!" This was the classic introduction played at the beginning of every episode of Welles' famous radio program, "The Shadow".
On the script are various other narratives of Orson Welles' work with his Mercury Theatre and his move from New York plays to Hollywood movies (mostly under the supposed "VOICE" character).