Lea Thompson remembers being snooty to Michael J. Fox on the Back to the Future set

Lea Thompson says it took a while to get comfortable with Michael J. Fox after he was hired to replace Eric Stoltz Back to the future.

Thompson, who played the mother of time-traveling 1950s teenager Marty McFly in the 1985 blockbuster opposite Fox, appeared on the latest episode of his podcast with host Steve Kmetko Still here Hollywood to talk about her career – including whether or not she got along well with Fox on set Back to the future.

“Probably not,” the 63-year-old actress admitted, “because I was friends with Eric Stoltz, who had just been fired.”

Of course, almost 40 years later, it's hard to imagine anyone else playing Marty. But while Fox was reportedly the first choice for the role, director Robert Zemeckis cast Stoltz when Fox was initially unavailable due to his role at NBC Family ties. After filming began in November 1984, the filmmakers quickly realized they had made a mistake and ended up replacing Stoltz with Fox.

Thompson explained that she had previously played alongside Stoltz in 1984 The wild lifeand played alongside him again in the 1987s Somehow wonderful. “So he was a friend of mine,” she said.

But that wasn't the only reason she was initially cold towards Fox.

“I remember being particularly snooty because there was a big divide between movie stars and TV stars at that point,” Thompson said. “I remember thinking, 'He's just a TV star and I'm a movie star.' I was there Jaws 3D.' I think it took me a while to warm up to him, but he was so funny and so much fun to play with.”

“I had already shot some scenes with Eric and then had to reshoot them with Michael so I could see that they were completely different scenes,” Thompson continued.

Somewhat counterintuitively, Thompson said that the fact that the filmmakers replaced Stoltz with Fox was just something they did more confident that Back to the future would be a hit.

“When we were filming and six weeks later they replaced Eric Stoltz with Michael Fox, I thought, 'Oh, they must like what they're doing because nobody does that.' “It’s very expensive,” she explained. “So I had a feeling, but no one knew, that it was going to be what it was.”

But Thompson recalled that the lineup change certainly had an impact. “You know, everyone always wants to say, 'Oh, wasn't that funny?' You know, that’s what people want to hear,” she said. “And it was very – it was a lot of pressure and it was a scary thing, especially after they fired Eric Stoltz. They said, “This is no fun and games.” This is big business and, you know, a big deal.”

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Nearly four decades later, however, Thompson says she remains friends with Fox and sees him at fan conventions a few times a year. “So I see him in the strangest situation ever, which is in front of 3,000 people,” she said. “And sometimes we go out to dinner as a group. It’s really nice to see him.”

She also praised the actor, who was diagnosed with Parkinson's disease in 1991, for his work raising awareness of the disease and raising money for research through his Michael J. Fox Foundation.

“This is really special for me because both of my brothers were diagnosed with Parkinson’s disease a year ago,” Thompson added.