Showrunner Roberto Aguirre-Sacasa initially considered Shipka to play the role of Betty Cooper on Riverdale. "Kiernan was iconic in Mad Men . . . I was like, 'Oh I wonder if she'd ever do Betty,'" he told Entertainment Weekly. Obviously, Lili Reinhart ended up with the role. However, Shipka made such a lasting impression on everyone that she began to be considered for the role of Sabrina before the script for CAOS was even written. After casting director David Rapaport said Shipka might be interested in the role as the show moved from The CW to Netflix, Aguirre-Sacasa began writing the script for Shipka. "For me it was sort of like, 'Okay she's Sabrina. I'm writing this for Kiernan,'" he told Entertainment Weekly.