However, speculation cropped up about the actor potentially appearing in Ezra Miller's upcoming DC Studios film centered on the Scarlet Speedster. Rumors have swirled that The CW actor will pop up in the film, potentially joining a collection of Multiversal cameos set for the costumed epic.
In the lead-up to the movie, some have even called for Gustin to take over as DC's big-screen Flash after Ezra Miller, but nothing has been officially mentioned about the actor's DCU inclusion as of yet.
Grant Gustin & The Flash Movie
A new Official Visual Companion (which appeared on Reddit) for DC's The Flash movie featured Grant Gustin's Arrowverse version of the hero, potentially hinting at his character showing up in the film.
Gustin is showcased on the cover alongside Ezra Miller's Barry Allen and a number of those takes on the Scarlet Speedster.
The Visual Companion is described as a "comprehensive collection of stunning images, behind-the-scenes stories, and interviews" centered around the film:
"Keep pace with the Fastest Man Alive with this compendium of facts and incredible images from the Super Hero’s landmark film debut! The Flash™: Movie Encyclopedia satisfies your need for cinematic speed on every page, with making-of details and behind-the-scenes profiles of the characters, locations, and artifacts seen on screen. Interviews with key cast and crew members offer a one-of-a-kind look at the creation of the highly anticipated new film. It’s the perfect gift for every fan who’s been waiting for DC’s iconic Scarlet Speedster to take the lead in a film of his own."
While not a confirmation of a Grant Gustin cameo in The Flash, it does add fuel to the fire that sparked up around the CW hero showing up.
Miller and Gustin previously shared the screen in some Flash-centric shenanigans, with the DC Studios' big screen version of the hero making a cameo in Gustin's Crisis on Infinite Earth CW Arrowverse event.
Speaking on Miller's cameo on The CW series, The Flash series executive producer Marc Guggenheim told Variety that it was a "phone call from [Warner Bros. boss] Peter Roth" that made the film-to-TV crossover happen:
"We were series wrapped on 'Arrow,' and we were wrapped on the whole crossover. We were in post and some episodes were locked, and some were soft-locked. I got a phone call from [Warner Bros. boss] Peter Roth saying, 'I know you’re locked, but can you put Ezra into the crossover?'”
He remembered telling Roth that despite having the "series wrapped" and everything locked in, "if [Roth was] telling [him] Ezra Miller can be in the crossover, [he] can make it happen:"
"And I said, 'Yes.' And he said, 'How, you’re series wrapped? And you’re wrapped on the crossover.' And I said, 'Yeah, I know, but if you’re telling me Ezra Miller can be in the crossover, I can make it happen.' I called Eric Wallace who who is the showrunner of 'Flash,' and he called up Grant Gustin — because the one thing that was our only concern was the thought we didn’t want to do it unless Grant was 100 percent onboard with it. And he was."
Luckily, Gustin was "incredibly enthusiastic and onboard" with the idea of Miller appearing. They then went ahead and shot everything, and because "no one leaked" the cameo, they "were able to keep it a surprise:"
"He was incredibly enthusiastic and onboard with it. And then we got on the phone with Ezra Miller and told him the scene I had written and he was completely into it. And we just went. We put together a unit of the 'Flash' crew on the 'Flash' set [since 'Arrow’s' team, which had produced the rest of the hour, was gone]. And much to our surprise, no one noticed Ezra Miller was in Vancouver and no one leaked it from the crew, which we appreciate. So we were able to keep it a surprise."
Is Grant Gustin in the Flash Movie?
Of course, just like was the way with Ezra Miller crossing over to the Arrowverse, Grant Gustin will not be 100% confirmed for The Flash until his character is up there on-screen.
However, there is plenty of evidence saying his Arrowverse take on Barry Allen will show up - at least briefly - in the DC blockbuster.
While the film has undergone significant changes recently when it comes to hero cameos, it feels like, if Gustin did film something, his cameo is safe.
This is especially knowing that Ezra Miller showed up in Gustin's Flash universe at one point. So a return of the favor only seems natural.
It was almost two years ago that Gustin's cameo was first reported by the Illuminerdi. But since then, things have remained fairly quiet.
Perhaps Gustin came in to film for a day or two, was on set for only a short period of time, and then was out of there, resulting in no pictures or anything to leak aside from this one initial report.
But one would think with all the test screenings the movie has been going through in the past year, something would have leaked if he was there.
If Grant Gustin is in the film will be answered when The Flash races into theaters on June 16.