The season is produced by Berlanti Productions, Warner Bros. Television, and DC Entertainment, with Robert Rovner and Jessica Queller serving as showrunners.

[citation needed] Barry Allen and Oliver Queen wake up as wanted criminals hunted by John Deegan as a black suited Superman while Kara is imprisoned at S.T.A.R.

After narrowly escaping Deegan, Barry and Oliver locate Cisco Ramon, who works as a mob boss with James as a henchman, and retrieve Superman from Earth-38.

Barry and Kara travel in opposite directions to slow the Earth's rotation in order to impede Deegan, despite Clark saying it will kill them.

On Earth-1, Oliver gets a call from Batwoman, revealing Deegan is in Arkham and has seemingly made friends with the Psycho-Pirate, who teases a future crisis.

At the Television Critics Association press tour in January 2018, The CW president Mark Pedowitz said he was "optimistic" and "confident" about Supergirl and the other Arrowverse shows returning next season, but added that it was too soon to announce anything just yet.

[75] Nicole Maines and April Parker Jones had been cast as series regulars and would portray Nia Nal / Dreamer and Colonel Lauren Haley, respectively, with the former being the first transgender superhero on television.

[95] The season was released on DVD and Blu-ray on September 17, 2019, with special features including the show's 2018 Comic-Con panel, deleted scenes and a gag reel.

The website's critic consensus reads: "Though it's a little tonally inconsistent, Supergirl's fourth season still soars thanks to strong, relevant writing brought to life by its charming cast.

"[120] IGN's Jesse Schedeen said of the premiere that, "After a disappointing finish to a generally underwhelming Season 3, it's good to see Supergirl quickly bouncing back this week.

'American Alien' sets the stage for a promising conflict to come, introducing memorable new villains and supporting characters and forcing Kara to confront the things she can't control in her city.

Club concurred with Schedeen's X-Men comparison, reflecting that over the seasons, "[Supergirl] has grown both more explicit and more nuanced in its handling of social and political issues."

"[123] The book Adapting Superman: Essays on the Transmedia Man of Steel includes the chapter "Forging Kryptonite: Lex Luthor's Xenophobia as Societal Fracturing, from Batman v Superman to Supergirl," which analyzes Lex Luthor's actions in Season 4 "as a representation exploring the cultural effects of encroaching xenophobia" from society to the family in the years following the 2016 United States presidential election.