In publicity around the making of Christopher Nolan's Dark Knight trilogy, co-writer David S. Goyer has recounted how the director initially resisted giving the villain Scarecrow his signature mask in 2005's Batman Begins. Nolan's insistence on realism — a mantra of "it has to be real" — clashed with the comic-book convention of masked super-criminals, and he questioned whether Dr Jonathan Crane, played by Cillian Murphy, needed to wear a mask at all. Goyer, a lifelong comics fan, held firm that the character had to have one, and Nolan relented on the condition that the script provide a plausible in-story reason for it.

The solution was to make Scarecrow's burlap sack mask a functional gas mask, fitted with a breathing apparatus so Crane could avoid inhaling the weaponised fear toxin he sprays from his sleeves. Costume designer Lindy Hemming dressed Murphy in deliberately ill-fitting, too-small suits with short sleeves and a small collar to create the illusion of an oversized head, echoing a scarecrow; the team produced over 100 sketches and 20 prototype masks before settling on a simpler, less cartoonish version of the comics design. The article also notes that Nolan and Goyer deliberately chose villains such as Scarecrow and Ra's al Ghul (Liam Neeson) because they had not previously appeared on screen, drawing on comics like Batman: Year One and The Long Halloween while avoiding characters already used in earlier films.