Michael J. Fox was the first choice to play Marty McFly, but he was committed to the show Family Ties. Family Ties producer Gary David Goldberg felt that Fox was essential to the show's success. With co-star Meredith Baxter on maternity leave, he refused to allow Fox time off to work on a film. Back to the Future was originally scheduled for a May 1985 release and it was late 1984 when it was learned that Fox would be unable to star in the film. Zemeckis' next two choices were C. Thomas Howell and Eric Stoltz. Stoltz impressed the producers enough with his earlier portrayal of Roy L. Dennis in Mask (which had yet to be released) that they selected him to play Marty McFly. Because of the difficult casting process, the start date was pushed back twice.Four weeks into filming, Zemeckis determined Stoltz had been miscast. Although he and Spielberg realized re-shooting the film would add $3 million to the $14 million budget, they decided to recast. Spielberg explained Zemeckis felt Stoltz was not comedic enough and gave a "terrifically dramatic performance". Gale further explained they felt Stoltz was simply acting out the role, whereas Fox himself had a personality like Marty McFly. He felt Stoltz was uncomfortable riding a skateboard, whereas Fox was not. Stoltz confessed to director Peter Bogdanovich during a phone call, two weeks into the shoot, that he was unsure of Zemeckis and Gale's direction, and concurred that he was wrong for the role.Fox's schedule was opened up in January 1985 when Baxter returned to Family Ties following her pregnancy. The Back to the Future crew met with Goldberg again, who made a deal that Fox's main priority would be Family Ties, and if a scheduling conflict arose, "we win". Fox loved the script and was impressed by Zemeckis and Gale's sensitivity in releasing Stoltz, because they nevertheless "spoke very highly of him". Per Welinder and Bob Schmelzer assisted on the skateboarding scenes. Fox found his portrayal of Marty McFly to be very personal. "All I did in high school was skateboard, chase girls and play in bands. I even dreamed of becoming a rock star."Christopher Lloyd was cast as Doc Brown after the first choice, John Lithgow, became unavailable. Having worked with Lloyd on The Adventures of Buckaroo Banzai (1984), producer Neil Canton suggested him for the part. Lloyd originally turned down the role, but changed his mind after reading the script and at the persistence of his wife. He improvised some of his scenes, taking inspiration from Albert Einstein and conductor Leopold Stokowski. Brown pronounces gigawatts as "jigawatts," which was the way a physicist would say the word,  when he met with Zemeckis and Gale as they researched the script (rather than with an initial hard "g", although both pronunciations are acceptable). Doc Brown's notable hunch came about because at 6 feet 1 inch (1.85 m) Lloyd was considerably taller than Fox at 5 feet 5 inches (1.65 m), and they needed to look closer in height.Crispin Glover played George McFly. Zemeckis said Glover improvised much of George's nerdy mannerisms, such as his shaky hands. The director joked he was "endlessly throwing a net over Crispin because he was completely off about fifty percent of the time in his interpretation of the character". Due to a contract disagreement, Glover was replaced by Jeffrey Weissman in Part II and Part III.Lea Thompson was cast as Lorraine McFly because she had acted opposite Stoltz in The Wild Life; the producers noticed her as they had watched the film while casting Stoltz. Her prosthetic makeup for scenes at the beginning of the film, set in 1985, took three and a half hours to apply.Thomas F. Wilson was cast as Biff Tannen because the producers felt that the original choice, J. J. Cohen, wasn't physically imposing enough to bully Stoltz. Cohen was recast as Skinhead, one of Biff's cohorts. Had Fox been cast from the beginning, Cohen probably would have won the part because he was sufficiently taller than F

Question: What personality did Fox have?
Answer: Marty McFly