Sister Alice (Tatiana Maslany) is based on evangelist Aimee Semple McPherson, also known as "Sister Aimee," a Canadian Pentecostal evangelist and media celebrity in the 1920s and 1930s. As demonstrated by the first scene of Sister Alice's sermonizing, McPherson pioneered the use of modern media in religious services, using radio to draw on the growing appeal of popular entertainment and incorporating stage techniques into her weekly sermons at Angelus Temple, an early megachurch.
In a small in-joke, when goaded by Baggerly, Perry reveals that he's a quarter Welsh. Matthew Rhys, who plays Perry, was in fact born and raised in Cardiff, Wales, and his first language is Welsh.
The character Sister Alice is supposed to have come from Saskatchewan. Tatiana Maslany was born in Regina, Saskatchewan.
The diner where Della takes Emily for lunch is Musso & Frank's Grill, a Hollywood landmark, also featured in "The Kaminsky Method" (2018-2021), "Ed Wood" (1994), "Once Upon a Time in Hollywood" (2019), "The Man Who Wasn't There" (2001), Ocean's Eleven (2001), and more.