Ben Affleck shares how Adam Driver saved his son's birthday

Adam Driver -- Kylo Ren to "Star Wars" fans -- made Ben Affleck's son's birthday unforgettable.

During a visit to "Jimmy Kimmel Live," Affleck explained that his 8-year-old, Samuel, believes "Star Wars" is real and couldn't understand how his dad had an opportunity to shoot a movie with Kylo Ren.

Affleck added that he mentioned his son's fandom to Driver, and asked him to shoot a video that he could play for Samuel at his birthday party.

Driver obliged, and then surprised Affleck by sending him "Star Wars" memorabilia for Samuel -- a gesture that ultimately saved the day, as Affleck's gifts failed to arrive on time.

"Adam made me a hero to my kid. And I will never, ever, ever forget it," Affleck said. "It's a really good lesson in doing those small gestures of kindness, because you have no idea. For [Driver], he's like, 'Yeah, send the Kylo Ren doll and the Kylo Ren LEGO and the Kylo Ren thing and the little picture of Kylo Ren signed by Kylo Ren.' It meant the f---ing world to [Samuel]. So much."

Watching him open them "was an incredibly moving and powerful moment," he added.

Affleck, 47, has three children with his ex-wife, Jennifer Garner: daughters Violet, 14, and Seraphina, 11, and Samuel. In a recent interview with ABC News, the actor, whose film "The Way Back" hits theaters Friday, said that he was disappointed that he and Garner divorced, especially because he "really didn't wanna be a split family with my children." He and Garner, also 47, married in 2005 and announced their separation 10 years later. She officially filed for divorce in 2017.

"I never thought I was gonna get divorced -- I didn't wanna be a divorced person," he said. "It upset me because it meant I wasn't who I thought I was. And that was so painful and so disappointing."

Today, he said, "I'm doing my very, very best."

"It has to be good enough," he continued. "I have to be the man I wanna be at this point. I don't have any more room for failure of that kind."