Cat Grant: All four of you standing there doing nothing, you look like the attractive yet non-threatening, racially diverse cast of a CW show.
Lena Luthor: I'm not a villain. I don't wanna kill Supergirl; I just want her to experience the same hurt she inflicted on me. And soon enough, she will.
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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