Brec Bassinger deliberately avoided watching the previous portrayals of Stargirl by Britt Irvin on Smallville and Sarah Grey on Legends of Tomorrow, since those versions were older and more mature, choosing instead to base her performance on the younger, more naive high-school version from the Stars and S.T.R.I.P.E. comic.

Geoff Johns described casting the lead role as a difficult process that involved auditioning hundreds of actresses before Brec Bassinger was chosen.

Neil Jackson initially thought the villain name 'Icicle' sounded silly, almost like something from My Little Pony, but Geoff Johns' pitch convinced him the character could be credible.

Geoff Johns compared the tone of Stargirl to 1980s films such as E.T. the Extra-Terrestrial and Back to the Future.

The series was originally ordered by the streaming service DC Universe in July 2018, before moving exclusively to The CW starting with its second season.

Legacy Effects built a practical, functioning version of the giant robot S.T.R.I.P.E. for use during filming.

Stargirl was reportedly the first Warner Bros. Television series to use previsualization, a technique more commonly used in feature films, handled by The Third Floor, Inc., drawing on Geoff Johns' experience working on Wonder Woman, Aquaman, and Shazam!.

Stunt coordinator and second-unit director Walter Garcia was specifically hired to give Stargirl's cosmic staff its own personality and make it feel alive during fight scenes.

The pilot episode's release was postponed by exactly one week, from an intended May 11 premiere to May 18, 2020.

When the series aired on The CW, roughly eight minutes were cut from each of the first two episodes to accommodate commercials, removing scenes like an extended hallway interaction between Courtney and Cindy Burman and a mysterious creepy janitor character played by Mark Ashworth.

In the Arrowverse crossover 'Crisis on Infinite Earths', Stargirl and her team were briefly introduced via archive footage, establishing that the show takes place on a new Earth-2 within the larger multiverse.

John Wesley Shipp appeared as an alternate version of Jay Garrick/The Flash, a role he originated on The Flash, to help connect Stargirl's universe with the wider Arrowverse.

Brec Bassinger reprised her role as Stargirl in an episode of HBO Max's Titans titled 'Dude, Where's My Gar?', a series set on a different Earth in the live-action multiverse.

The pilot episode was tied for the second-best series debut on The CW for the 2019–20 season, and was the network's best summer series premiere since Whose Line Is It Anyway? season nine in 2013.

After the show's cancellation, it was revealed that a planned spin-off centered on Infinity Inc. would have followed Shade, Jennie, and Todd searching for other children of the original JSA members.