The longtime friends were guests on Wednesday's episode of The Tonight Show Starring Jimmy Fallon, and showed two photos of themselves goofing off in a photo booth at age 17.
"Hard not to see that those guys are going to make it," Affleck quipped of his and Damon's younger selves.
"Yeah, those guys, clearly have star written all over them," Damon joked. "I think it's the matching puka necklaces that give it away."
The pals also shared a photo from the premiere of Good Will Hunting in 1997, with Affleck joking, "You wouldn't imagine that those two idiots would still be around."
Affleck and Damon are together again for The Last Duel, the first film they've co-written and co-starred in since Good Will Hunting. They both opened up to ET about their long-lasting friendship at the New York premiere of the highly anticipated movie.
"Over those 25 years, Matt and I have been friends and worked together so it doesn't feel like, 'Oh, I haven't seen this guy in 25 years,'" Affleck explained. "But it is nice! It's cool to be doing another movie with him."
Damon added that he was surprised to have made it so far in his career.
"If you told me 25 years ago [that we'd be here tonight], I would be like, 'We made it? We are still working? OK good!'" he joked.
As for working together on The Last Duel, Affleck added, "We loved it, and we definitely want to do more."
The Last Duel hits theaters on Friday.