There are lots and lots of details that will take repeated viewings to catch. One of them is a shout out from executive producer Frank Marshall to his assistant Mary.
Apparently, Mary was worth it enough for the executive to push a reference in the first film. After Marty’s failed audition for the battle of the bands, he and his girlfriend Jennifer are walking down the street and discussing Marty’s direction in life, they pass a car that has the license plate “For Mary,” and this is recognized as a nod to Mary Redford, Marshall’s personal assistant.
A Nod to Kubrick
No matter what you think of Stanley Kubrick's movies, they have a unique style that sticks with you, and in-jokes to his movies will appear in a lot of other works.
For instance, CRM 114, the huge monitor that blows Marty through a wall at the beginning of "Back to the Future", is a fictional device used in "Dr. Strangelove", and is also the name of an experimental chemical in "A Clockwork Orange", two well-known Kubrick films. 114 is seen in lots of different films, such as "Star Wars" or "Men in Black", as a geeky reference to Kubrick or film history in general.
Have You Heard the News?
Huey Lewis and the News is a beloved band that contributed plenty of music to the films, including “The Power of Love” from the first film. He also makes an appearance in the first film as a school teacher during Marty's audition for the school's battle of the bands.
Amusingly, Marty and his band (“The Pinheads”) choose a Huey Lewis and the News song to play. Huey Lewis stands up, brings a megaphone to his lips, and tells the band they were “too darn loud.” If you either didn't recognize Lewis or the song, it might have gone over your head.
Set to be President
On the wall of Hill Valley High School in 1955, there's a sign that appears on the wall that is begging you to vote for Ron Woodward for senior class president.
It turns out Ron Woodward was the name of a key grip, in charge of rigging and lighting for the movie, and the set decorators used his name on the poster as a joke. After standing up to Biff Tannen, George McFly wonders if he should run for class president, which means he might have tried to go up against Woodward.
Zemeckis Self-References
The town of Hill Valley is a place of many references, and though this one might be a coincidence, we could one hundred percent believe that it was intentional.
In the scene where Marty hitches a ride on the back of a pick-up truck on his skateboard, he passes a “Used Cars” sign. It's nothing out of the ordinary, but “Used Cars” is actually the title of the first film that Robert Zemeckis and Bob Gale collaborated on, a satirical black comedy released in 1980.