Answer: Back to the Future
"Back to the Future" tells the story of young Marty McFly (Michael J. Fox), who travels back in time, in a time machine, invented by his very eccentric best friend, Dr. Emmett Brown (Christopher Lloyd). Whilst in the year 1955, Marty accidentally stops his parents from meeting. Unless he can quickly get his mum to meet, and fall in love with his hopeless father, Marty won't be born, 13 years later. Marty enlists the help of the Dr. Brown of 30 years earlier. The tag line explains how Marty has turned up at his home, only he has turned up 30 years earlier, which is 13 years before his birth.