The Faithful - S3-E4
Trivia: James and Winn find a meeting of Coville and his followers to be "a little cult-y." Melissa Benoist plays Rachel Koresh, the wife of cult leader David Koresh, in the miniseries Waco, a dramatization of the Waco siege - the 1993 standoff between the ATF and FBI and Koresh's Branch Davidians that lasted 51 days and resulted in 86 deaths.
Answer: For one, it's usually cheaper to film in Vancouver because of the tax breaks. But all the CW Arrowverse shows (with the exception of "Black Lighting") are/were filmed in Vancouver. So it makes it easier and cheaper for sharing set designs, crossovers, etc ("Black Lightning" filmed in Vancouver during its crossover). Originally "Supergirl" wasn't part of the Arrowverse when it was on CBS, but it was too expensive to produce and wasn't reaching the wider audience the CW shows had. So CBS moved it to its sister company, The CW.
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