Working Girl, starring Harrison Ford as Jack Trainer and Melanie Griffith as Tess McGill depicts a scene showing Jack and Tess in bed having a discussion on how Jack acquired a scar on his chin that Tess has noticed while she is stroking his face with her fingertips:
TESS: How'd you get this scar?
JACK: Some guy pulled a knife in Detroit.
TESS: Really?
JACK: No. No. I was 19 and I thought it'd be cool to have a pierced ear. My girlfriend stuck the needle through and I fainted and hit my chin on the toilet.
It is well known that Harrison Ford has an actual scar on his chin due to a car accident when he was younger. Steven Spielberg actually incorporated the scar into the script for another one of Harrison Ford's films, Indiana Jones and the Last Crusade.
Unlike the explanation of the scar in the Indiana Jones series, the discussion surrounding the scar in Working Girl does not have anything to do with the plot of the movie and does not seem to add anything significant to the story.
What was the reasoning behind the filmmakers decision to incorporate Harrison Ford's real life scar into the script of the film? Is there any evidence to indicate that filmmakers chose to add this into the script after Harrison Ford was cast in the film?