Here's how 'Transformers: Rise of the Beasts' pulled off that 'G.I. Joe' crossover

Warning: This post contains spoilers for Transformers: Rise of the Beasts.

Three weeks — that's how recently the creators of Transformers: Rise of the Beasts locked in the surprise ending that features the long-awaited meet-up of Hasbro's biggest toy lines: Transformers and G.I. Joe. Not only does that reveal set the stage for an eighth Transformers film on the back of Beasts's history-making opening weekend, it also teases the beginning of a shared Hasbro Cinematic Universe.

"I wanted a button on the end that said where were going," director Steven Caple Jr. tells Yahoo Entertainment now. "We got it at the very last minute. ... That's scary now that I think about it!"

Here's how the reveal goes down. In Rise of the Beasts's closing minutes, the movie's human hero, Noah Diaz (played by Anthony Ramos), meets with Agent Burke (Michael Kelly) a government agent who wants to thank him for saving the world alongside Optimus Prime's virtuous Autobots. At the end of their conversation, Burke offers Noah a job, and passes along a business card with the name of his top secret outfit: G.I. Joe.

Watch our interview with the Transformers: Rise of the Beasts cast and crew about the G.I. Joe crossover teased at the end of the movie

According to Ramos and Caple, they shot two different versions of that scene with two different business cards just in case Hasbro vetoed the G.I. Joe reveal. In the alternate take, the card said "Sector Seven" — a reference to the paramilitary organization that played a role in Michael Bay's Transformers movies. Rise of the Beasts is set in the 1990s, before the events of those films and before the three standalone G.I. Joe features that Hasbro has previously released: 2009's The Rise of Cobra, 2013's Retaliation and 2021's Snake Eyes.

"Steven and I talked about it before shooting the scene," Ramos remembers. "He was like, 'We're trying to merge the worlds, and there are a lot of people that need to approve that." That list included Bay, executive producer Steven Spielberg, producer Lorenzo di Bonaventura and everyone at Hasbro. "It only got greenlit three weeks ago," Ramos says with obvious amazement. "When I flipped that card, I was like, 'Please god, let this be true.' There's so much we can do with these worlds."

The idea of bringing together the Transformers and the Joes dates back to 2015, when Hasbro and Paramount reportedly took a serious run at constructing a Hasbro-based movie universe that would also have tied in other toy lines like the Micronauts and ROM. But those plans fell by the wayside as di Bonaventura — who overseas both the Transformers and G.I. Joe movie franchises — instead tried to reboot the Joe series with Snake Eyes. This time around, though, the producer was onboard with merging the cinematic worlds, replicating a crossover that has already happened in comic books.

"We've thought about it for awhile for sure," di Bonaventura says. "It was an obvious thing to do, but we didn't want to burn through all the mythologies too quickly. We've been trying to introduce new elements, and in this case we introduced the idea that the Joes can enter. One of the things that has kept the franchise feeling fresh is that we don't plan [ahead]. We don't plan ahead of purpose, because we want to see how the audience is going to feel about things."

To that end, di Bonaventura declines to specify how big a role G.I. Joe will play in a Rise of the Beasts follow-up or if that movie will necessarily lead into the continuity established by the previous Joe pictures. "I think it will tie into the mythology. ... There's plenty there that we haven't explored," he says. "But this thing was decided at the very last minute, because we weren't sure how everybody would feel about it, including ourselves! But when we saw the movie, we were like, 'OK, that really works.'"

It's no secret that the standalone G.I. Joe franchise has struggled to match the success of the Transformers movies. The Rise of Cobra and Retaliation both fell below $400 million at the worldwide box office, while the pandemic-affected Snake Eyes only managed to make $40 million around the globe. Di Bonaventura thinks that a surplus of characters has been one of the elements that has held those films back from becoming as big as the ones starring Hasbro's giant transforming robots.

"We have to be careful of doing ensemble movies," the producer says. "Six or seven characters is [about right] — you start going past that and they have to be minor characters because you just don't have the screentime. Maybe in the past we might have made a mistake or two [about that]. Looking ahead, we're going to try to keep the number of things that we're dealing with from a character point of view to a relative maximum."

For the record, Caple says that he'd love to be the one that finally unites the G.I. Joe team and the Transformers onscreen. "I have a lot of ideas for where we're going in the future — a lot of new vehicles, new characters, new plots and new dilemmas. The universe has expanded overall and I feel like they can really incorporate and add new life to the franchise."

"I haven't thought about whether or not the next film should tie into the other Joe films," Caple continues. "I'm always the one to say, 'Let's do something fresh.' I will say that my favorite G.I. Joe cartoon is G.I. Joe: Renegades, which is about the outcasts of the Joes. That might be interesting — that way me don't have to mess up anything in the lore that happened in the other G.I. Joe movies and do our own thing. I think we could create something really cool."

Both Ramos and co-star Dominique Fishback are ready to squad up with the Joes as well. "I used to have all the toys, man," the In the Heights star says. "I had G.I. Joe toys, I had Transformers toys. I'm just so hyped and excited."

"I was telling Steven that since my character gets introduced to the fight in Rise of the Beasts, she's going to get training in between films," Fishback adds with a laugh. "She doesn't know what life is gonna bring her now! She wants to be prepared, and I think that can help her easily put on a G.I. Joe suit and kick some butt." Like the Joes always said, knowing really is half the battle.

Transformers: Rise of the Beasts is currently playing in theaters.