He hunts out Doc's past self in order to help him devise a plan to return Back To The Future.
Boasting a large number of hits from both the 1980's and the 1950's, the appeal for the film was evident right away. Opening with The Power Of Love, the film stretches from the lazy Ballad Of Davy Crocket to the bouncy Johnny B. Goode which are all famous songs from their respecitve eras.
The casting was genius - the irreplaceable Christopher Lloyd's face of Doc is one of the most memorable in Hollywood, while Michael J. Fox does a stirling job to keep the lead role as Marty McFly when he could so easily have been overshadowed by his colleague.
Of course there are parts of the film that are unrealistic, and these are just airbrushed over in comedy that makes the film all the more amusing. If it took itself too seriously then it just wouldn't work. Luckily, director Robert Zemeckis' ability to know when to stop laughing at yourself and when to start telling a story helps to keep the story on track at all times.
A definite must-see.