Marty McFly never tells his parents he traveled through time to bring them together in Back to the Future, but George had more than enough clues to piece it together. When Marty goes back in time and unwittingly bumps into his parents, he doesn’t tell them he’s their son from the future. Lorraine assumes his name is Calvin Klein, because it’s written in his underwear, and he just rolls with it. He pretended Doc Brown was his “Uncle Doc” and he made sure his parents fell in love without revealing he came from the future.
But Marty didn’t do a flawless job of hiding his tracks. He may not have outright said that he came from the future, but he did use some of his knowledge of the future to ensure that George would ask Lorraine to the school dance. When that stuff came to pass in the years that followed, it must’ve tipped George off. Neither version of George ever revealed on-screen that he figured out his son was a time traveler who visited him in 1955, but based on all the evidence, he had to have known.
After Watching Star Trek & Star Wars, George McFly Must Have Become Suspicious
Something Must’ve Clicked When He Heard
Why Marty McFly’s Father Had To Realize Time Travel Was Real After Back To The Future
