'The Fall Guy' director explains how he pulled off that famous cameo

• Warning: Spoilers ahead for "The Fall Guy."
• Director David Leitch told Business Insider how he landed the movie's big cameo.
• He's known this star since his first big movie.

"The Fall Guy" is full of star power, with the likes of Ryan Gosling, Emily Blunt, Hannah Waddingham, Winston Duke, Stephanie Hsu, and Aaron Taylor-Johnson gracing the screen for two hours.

But by the end of the movie, director David Leitch blesses us with one more big-name star: Jason Momoa.

"The Fall Guy" is set around the production of a big-budget sci-fi epic titled "Metalstorm," which stars Aaron Taylor-Johnson's character, Tom Ryder, and is directed by Emily Blunt's character, Jody Moreno.

After Ryan Gosling's stuntman character, Colt Seavers, uncovers the nefarious acts done by Ryder, in the movie's conclusion, we see that Moreno was able to complete "Metalstorm" thanks to the recasting of Momoa in the Ryder role.

Sporting a cowboy hat and samurai sword, the "Aquaman" star kicks alien butt as explosions happen all around him.

It turns out Momoa is an old friend of Leitch's.

"Jason and I go way back to his days when he was Conan," Leitch told Business Insider, referring to the 2011 movie "Conan the Barbarian," which marked Momoa's first major lead role. "I directed the second unit on that movie and we became good friends."

The two stayed in touch, and it so happened that as "The Fall Guy" was shooting in Australia, Momoa happened to be on that side of the world shooting in New Zealand.

"I just reached out and asked if he would come over for a day, and without blinking, he flew in and out on the same day," Leitch said, noting that Momoa showed up on his only day off from his own project to shoot the cameo.

"He showed up, and we put him in the cowboy costume, and there are explosions going on around him," Leitch said. "He came up to me and said, 'Only you, Leitch, would have me do this.'"

David Leitch is no stranger to pulling off big-name cameos for his movies. For "Deadpool 2," Brad Pitt shows up as Vanisher; in "Hobbs & Shaw," Kevin Hart makes an appearance; and for "Bullet Train," both Channing Tatum and Ryan Reynolds pop up on screen.

"The Fall Guy" is in theaters now.