The working title for Back To The Future Part II was called "Paradox" which ironically does happen in the movie lol.
A big question that people have always asked about Back To The Future is why is it when Marty goes back to 1985 is why his parents don't remember him from 1955.
In the first draft of the script when Marty comes back to 1985 his father was supposed to look at a old photo taken from 1955 and when he realises the guy he met in 1955 looks like his son he was supposed to shake his head and say nah it can't be and walks away.
Back To The Future Part 2 got the idea of being a darker movie from Empire Strikes Back.
The Long Riders(1980)
It is a notable film in part due to the decision to cast four sets of actor brothers as the real-life sets of brothers:
The Keaches: Jesse James (James Keach) and Frank James (Stacy Keach)
The Carradines: Cole Younger (David Carradine), Jim Younger (Keith Carradine) and Bob Younger (Robert Carradine)
The Quaids: Ed Miller (Dennis Quaid) and Clell Miller (Randy Quaid)
The Guests: Charley Ford (Christopher Guest) and Robert Ford (Nicholas Guest)
Originally Jeff Bridges and Beau Bridges were going to play the Ford brothers but they could not fit it in their schedules.
Although John Younger is portrayed as a cousin of the Youngers, he was a brother.
The roles of Jesse James and his son, little Jesse, are played by father and son, James and Kalen Keach.
Edward Bunker who plays Chadwell in the Northfield bank robbery was actually, among many other things, a convicted bank robber.
James Keach(Orville Wright) and Stacy Keach(Wilbur Wright) previously played brothers in NET Playhouse: The Wright Brothers(1971).
A little Easter Egg in Back To The Future Part 2, the scene in 2015 where the Marty Mcfly of 2015, Marty Mcfly Jnr and Marlene Mcfly are sitting at the table getting pizza. You'll notice that the pizza is half vegetables and half pepperoni and Marty Mcfly Jnr peels off pepperoni the joke with is that Michael J Fox is vegetarian.
The Johnny Cab in Total Recall is voiced by actor Robert Picardo who played the Doctor in Star Trek: Voyager. The face of Johnny was also based on the actor too.
Actor Brent Spiner who played Lt Commander Data on Star Trek: The Next Generation was the voice of the Joker on the animated series Young Justice which is now back for third season.
The movie Face-Off was originally written for Sylvester Stallone and Arnold Schwarzenegger.