In the scene you're referring to, Harrison Ford (playing Indiana Jones) is battling a sword-wielding adversary in a marketplace. Originally, the scene was written as a long, choreographed sword fight. However, Ford was suffering from dysentery during filming and was simply too weak to perform the fight scene.
The director, Steven Spielberg, decided to change the scene and have Indy simply shoot the man instead. This resulted in the iconic line, "It's not the years, honey, it's the mileage," and the scene became known for its humor and quick resolution.