10 More Glaring Plot Holes You Didn't Realise The Movie Actually Solved
3. Why Didn't Marty's Parents Recognise Him As Calvin Klein? - Back To The Future
Every single story that encompasses some sort of time travel will leave itself open for scrutiny, even arguably the most famous and popular one of all time. However, one of the biggest sticking points with Back to the Future isn't even a real flaw.
Marty McFly (Michael J. Fox) goes back in time and helps his parents get together in the past under the guise of Calvin Klein, then Marty grows up to look exactly the same as he did as Calvin Klein. The internet loves to point out that surely his parents should recognise that the two supposedly separate people are identical and that questions would be raised.
In short, the answer is no. It's not like Calvin was a close friend or family to the couple. The movie shows that he was only in their lives for a grand total of eight days, and so by the time they have Marty years later, chances are they wouldn't remember what Calvin looked like well enough to question it, if at all.
Back to the Future screenwriter Bob Gale added to this explanation when speaking to the Hollywood Reporter, making the very good point that if the choice is between thinking their son travelled back in time or that there is a slight resemblance between him and someone they knew years ago, if they remembered what he looked like at all, they will probably just assume the latter and get on with their lives.