Back To The Future 3 - How Did He Fall In Love With Clara?
When Marty and Doc save Clara from falling into Clayton Ravine, they are out to check on the railroad track that they will be pushing the time machine on. They hear Clara screaming and then save her from falling. Well then how did Doc fall in love with her when Marty wasn't there. The tombstone says "erected in eternal memory of his beloved Clara", but she would have just died before he actually met her, unless he just so happened be out looking at the track for no apparent reason when she was about to fall. Pretty coincidental.