Harrison Ford was originally used to find Han Solo, not become him
Although Harrison Ford is such a perfect marriage of actor and character in the role of Han Solo that casting him in hindsight seems like a no-brainer, it makes sense why Lucas was reluctant to consider the actor for Star Wars his performance as Bob Falfa in “American Graffiti”. Though there are flashes of Ford’s trademark charm and intensity in the character (and of course Ford’s natural, rugged beauty is put on great display), Falfa is ultimately an antagonistic and somewhat pathetic character, a drag racer’s local bully whose arrogance exceeds his Capabilities.
When it came time for Lucas to start casting “Star Wars,” he (infamously) pooled his resources with sidekick Brian De Palma, who began casting his adaptation of Stephen King’s “Carrie” during the same sessions . These auditions were random enough that even Mark Hamill, the future Luke Skywalker, was confused as to which film he was actually trying to audition for.
Still, Lucas provided some structure by using Ford as the “slide” (as the director put it in a vintage interview) for the other actors auditioning for Luke to proofread. Since many of Luke’s audition scenes were shared with the Han Solo character, Ford most often read Solo’s role for the various Lukes, and as Lucas recalled, this landed the actor the role:
“And I was shooting the screen tests, and you know, when you look at the screen tests where he’s playing the role and the other actors who were up for the role to play the role, there was just no question as to who was the best. And , you know, so I hired him for Star Wars.”