'The Flash' showrunner on how that Booster Gold surprise came together for midseason premiere

Though the various shows which comprise the Arrowverse over on The CW have been back in action for a while now, the pandemic era has still taken one of their defining qualities from us for the last couple of years. Since the pandemic has made shooting schedules a little tighter and a lot more uncertain, the shows within the fictional small-screen universe have found it harder and harder to do crossover episodes of any kind, because there's just no guarantee that one show will be able to keep up with the other in terms of airdates. 

Well, on this week's midseason premiere on The Flash, that changed just a little bit, with a small moment that could end up reverberating in a big way across Barry Allen's show and maybe even all the other Arrowverse series.

**Spoilers for The Flash midseason premiere ahead!**

This week's episode, "Impulsive Excessive Disorder," featured a scene in which Barry and Iris' future children, Bart (Jordan Fisher) and Nora (Jessica Parker Kennedy) rush to the Flash Museum in the year 2049 because they think something may have gone horribly wrong with the timeline after they got back from seeing their parents renew their vows in 2021 (because hey, it's a comic book show). When they get there, as they look for clues as to what went wrong with time, they see a newspaper headline touting the achievements of none other than Booster Gold (Donald Faison) in the museum archives. 

Bart and Nora then spent the rest of the episode working to set things right on the timeline, events which don't seem to have had anything to do with Booster, but that Easter egg still stuck out to a lot of fans. See, Booster was just introduced into the Arrowverse two weeks ago, over in the season finale of Legends of Tomorrow, and now he's making a photo cameo on The Flash. It's not a full-scale crossover, but it's a start. 

Speaking to Entertainment Weekly, Flash showrunner Eric Wallace explained how it went down.

"It was just a kind of a fun coincidence," Wallace said. "I was in post working on episode 806 and I knew the kids, Bart and Nora, would be looking at future things in the Flash Museum. And the head of post for our show and for Legends is the same person, Geoff Garrett. He happened to mention, 'Oh, by the way, don't tell anybody, but Booster Gold is going to be appearing in the finale of Legends.' I'm big Booster Gold fan, and I went, 'Hey, have they cast that person yet? I have a crazy thought. What if we see our kids in this episode looking through newspapers and we see whoever you guys have cast really fast, kind of a connected thing?' And he said, 'Well, it's funny you should mention that, Eric, because the finale of Legends airs the week before Flash returns.'"

From there, Wallace put in a call to Legends showrunner Phil Klemmer and Donald Faison himself, just to get them to sign off on the cameo. Less than a day later, Booster was suddenly appearing in both shows, because things move fast on The Flash.

So, does that mean Booster is set to be the bridge that unites these shows in a crossover once again? Not necessarily, but Wallace and company are already laying the groundwork for what he's teasing as a different kind of Flash finale coming later this year. Want clues? Go back and watch the five-part "Armageddon" event that the series aired back in the fall. 

"Look at those things. If you want to get ready for the new season, go back and re-watch 'Armageddon' on the CW app," Wallace said. "We had a master plan and 'Armageddon' was only part one of three parts. If you want to divide the season into three: 'Armageddon' part one; the middle Graphic Novel, part two; and [then] our big finale in which we're not trying to outdo ourselves from last year. We're trying to do something a little different that is a little wilder and perhaps a little more terrifying. Team Flash is about to go to through some very intense times. I'm not kidding. It's about to get hardcore."

The Flash airs Wednesdays on The CW.