I mean, George Lucas hired Harrison Ford as a carpenter because he wasn’t interested in doing a second movie after American Graffiti.

Mark Hamill was probably the most experienced member of the original cast because he had done some TV work.

Natalie Portman had starred in four features before Star Wars and McGregor had done more than ten.

I think Mark Hamill has mentioned before that there were times when Harrison Ford pushed back against Lucas that Han Solo would never say the lines he was given, and got them changed as a result.