Other mistake: During an argument, Maggie's father mentions the border wall being built to keep people from entering the country illegally. This is obviously a reference to the real-life presidency of Donald Trump, but within the show's continuity, his comment doesn't make sense: in "Resist", the penultimate episode of season two, it's revealed that President Olivia Marsdin is literally an alien from outer space, and earlier in the season in "Welcome to Earth", she signed an executive order offering aliens such as herself full citizenship if they so desired it. If she's that tolerant of extraterrestrials, it seems unlikely that she'd be so intolerant of foreign immigrants as to resort to such an extreme action in foreign policy like building a wall on the border.
Supergirl (2015)
Episode list - season 3
Starring: Calista Flockhart, Melissa Benoist, Mehcad Brooks, David Harewood
More mistakes in Supergirl
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.
The Adventures of Supergirl - S2-E1
Trivia: When Cat Grant walks to her office door, she screams out, "Miss Teschmacher!" In Superman and Superman 2, Miss Teschmacher was Lex Luthor's assistant and him screaming her name was his way of getting her to run to him.
Question: Does Kat ever wise up again to Kara's secret? That and why did she (Flockhart) leave the show only to come back?
Answer: Yes, s02e22. As Kara leaves her office, she said "go get them, Supergirl" to herself. After season 1, the show switched from a CBS production to a CW production and filming moved from L.A. to Vancouver. Flockhart isn't really a fan of traveling to shoot, and didn't want to be away from her family for so long.
Bishop73