Christopher Lloyd was not thrilled when, months into filming, the entire Back to the Future crew was summoned to an impromptu meeting, where they were informed Eric Stoltz had been fired from the picture and Michael J. Fox would be taking over as the lead, Marty McFly.

In a career retrospective with GQ published Monday, Lloyd opened up a bit about one of the most famous recastings in Hollywood history.

It is common knowledge for most Back to the Future fans that Stoltz was let go after six weeks of production because the filmmakers thought he was just not the right fit for the role. A deal was struck for Fox to work on the picture at night and film his popular sitcom, Family Ties, during the day.

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Lloyd, who starred as scientist Dr. Emmett Brown, told GQ he was shocked by the switch and had serious reservations, at least initially.

“They just decided that they needed somebody with a comic flair,” Lloyd said. “Stoltz is a wonderful actor. I had no idea the change was coming. My biggest fear, because I was really working to get Doc right, I thought, ‘I don’t know if I can get it up to do [all the scenes over] again.’ So I was worried about it. But, it all worked out.”

Of course, the duo were dynamite together and remain close pals to this day. Stoltz has never publicly discussed Back to the Future.

Lloyd’s concern is better understood when, later in the retrospective, the actor explains that while making One Flew Over the Cuckoo’s Nest, after a break in production he struggled to recommit to the Max Taber character. It took a chat with star Jack Nicholson for him to get back into the groove.

Lloyd also shared an interesting anecdote from his time on the classic sitcom Taxi, on which he played the iconic Jim Ignatowski. Lloyd explained that the show shot on Fridays in front of a live audience. And he recalled one moment in particular where a scene was not working.

“Someone came up [with the joke] — it wasn’t a writer; it was someone up in the ropes — and bingo! It worked,” Lloyd said. The classic joke in question is when Jim is taking the written part of a driver’s test, and he asks what a yellow light means. Bobby (Jeff Conaway), who is helping him cheat, whispers, “Slow down,” to which Jim repeats the question at a snail’s pace.

Watch the entire Lloyd career retrospective below.