Since concluding in 1990, the Back to the Future trilogy remains one of the few classic film franchises without a sequel or reboot. While the prospect of a fourth film in the series has been addressed in the past, franchise writer Bob Gale recently pointed to Michael J. Fox's health and an agreement with Steven Spielberg as the two main reasons why another sequel will never happen.

The original Back to the Future followed Fox's Marty McFly on a series of misadventures after he accidentally traveled from the '80s to the '50s in a DeLorean time machine created by his friend and mentor, Doctor Emmett "Doc" Brown. Despite threatening his own existence by derailing the fateful meeting between his parents, McFly is able to get his parents to fall in love and return to the 80s with the DeLorean intact. However, McFly's reunion with his girlfriend is short-lived when Doc Brown cuts his visit to the year 2015 short and returns with a dire warning regarding the future McFly children, leading to another journey across multiple time periods in Back to the Future Part II and Part III.

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Shortly after the trilogy concluded, Fox was diagnosed with Parkinson's disease and has since become an advocate for research on the degenerative disorder, helping to fund the search for a cure through The Michael J. Fox Foundation. During an interview with The Collider Podcast, Gale noted that Fox's health and age are among the reasons why he believes audiences don't want to see a fourth Back to the Future film. "We told a complete story with the trilogy. If we went back and made another one, we'd have Michael J. Fox, who will be sixty next year, and he has Parkinson's Disease. Do we want to see Marty McFly at age sixty with Parkinson's Disease? Did we want to see him at age fifty with Parkinson's Disease? I would say 'No, you don't want to see that," he explained. Recasting Marty is also out of the question according to Gale, who said, "you don't want to see Back to the Future without Michael J. Fox. People say, 'Well, do it with somebody else.' Really? Who are you going to get? All you’re gonna do is beg comparisons to the originals, and you're not going to match up. And we've seen this repeatedly with sequels that go back to the well after many, many years, and they go 'Ah, well, The Phantom Menace, maybe my life would have been better if I hadn’t seen it.'"

While  Back to the Future would be far from the only franchise to be revived decades after the most recent installment, Gale stated there is currently no creative incentive to produce another film. "We didn't want to be those guys who did a movie that was basically a money grab," he said. "Universal says to us, 'You guys would make a whole lot of money,' but we're like, 'Well, we've already made a whole lot of money with these movies, and we like them just the way they are. And as proud parents, we're not going to sell our kids into prostitution.'" The fact that Steven Spielberg and Amblin have agreed not to produce another Back to the Future film without the blessing or involvement of the original creative team is another reason why there will never be a fourth film in the series, according to Gale.

Pointing to Fox's condition as one of the reasons why a Back to the Future sequel will never happen may be odd to some, considering the Canadian-born actor has continued to appear in film and television projects since his diagnosis. One of Fox's most recent roles was an antagonistic Washington attorney named Ethan West in the second season of ABC's Designated Survivor.

On the other hand, Gale's point on sequels to popular franchises being released far past the time when there was a demand might be well-taken. In 2008, Indiana Jones returned to the silver screen for a fourth but much-maligned adventure, and Back to the Future fans may want the film series to avoid a similar fate by leaving the largely well-regarded trilogy alone.

Back to the Future is now available on Netflix.

MORE: Four Prequels That Are Better Than Their Predecessors

Source: Collider