The upcoming Arrowverse crossover event between Stargirl and The Flash will be fixing a Jay Garrick problem that relates to his comic origin. Stargirl tells the story of Courtney Whitmore discovering her inner hero. But as she does it, Courtney also revives iconic DC Comics team the Justice Society of America. With mantles such as Wildcat, Doctor Mid-Nite, and Hourman being picked up by new heroes, Stargirl is building another super-team for The CW. While the series was initially a DC Universe original, a while before its premiere, The CW ended up being its second parent as Stargirl aired on both platforms at the same time.
But for Stargirl season 2, things are changing up quite a bit. With DC Universe no longer being a home for original DC dramas, The CW will become Stargirl's only network going forward when it premieres season 2 later in 2021. When the series was initially being made, it wasn't eyed to be part of the Arrowverse but, thanks to Crisis on Infinite Earths, the Multiverse map for DC live-action properties was rebooted, including Earth-2. Now, Earth-2 has become the Stargirl universe as her team appears in a brief cameo during the 5-part event. Following on from that, Stargirl season 2 will be setting up its first crossover event with the Arrowverse through The Flash.
After having played the role on The Flash for several seasons, John Wesley Shipp will portray Jay Garrick in Stargirl season 2, but with a twist. Originally, when Jay was introduced, he was established to be a citizen of Earth-3. The last time fans saw Earth-3 was during The Flash season 6 when Barry Allen visits Jay's world for consulting on the coming Crisis. However, if the Arrowverse were to look at the traditional DC Multiverse map as portrayed in the comics, Earth-3 isn't actually the home of the Golden Age Flash. In the DC mythology, Earth-3 is an alternative reality where the heroes are the villains, operating as the Crime Syndicate of America and the villains are the heroes. But that wasn't the case with Arrowverse's Earth-3 where instead it was just the home of Jay Garrick and his villains.
Earth-2 has, as portrayed as on Stargirl, been the universe where the JSA was retroactively established to exist at. Prior to Crisis on Infinite Earths, Earth-2 was a combination of elements from the 1940s as well as layers of the 21st century. However, there was never a Jay Garrick there as Hunter Zolomon a.k.a. Zoom posed as the Earth-3 hero on Earth-2. But thanks to the 2019 crossover, not only has Stargirl gotten a proper Earth designation, but it also gave the writers a chance to reimagine Jay's background. In addition to that, the Arrowverse has now paved the way for Earth-3 to get a more comic accurate representation while also opening up the doors for the Crime Syndicate to show up one day.
While he'll be established as the Golden Age Flash in the crossover episode, it'll now be depicted as if he was always from Earth-2. All that is known so far about Shipp's guest spot is that his character will be part of a "pivotal flashback" episode. But it's always possible that he'll be revealed to be alive in the present time. It would be a waste of Shipp's talent and character if he somehow isn't part of what's going on in the current timeline on Stargirl. With no premiere date set for Stargirl season 2, only time will tell when fans will get to see him this year as he's scheduled to appear in the 9th episode of the DC drama when it crosses over with The Flash.