At the start, the mall is called Twin Pines mall. When Marty returns, it's Lone Pine after running over the pine tree at Peabody's Farm.
In the first 1985, you can see the ledge of the clock tower is intact
After Doc broke it in 1955, the broken bit remains there in the future
Eric Stoltz was first cast as Marty McFly, but was let go very late into shooting with most of the movie completed
This is one of the clocks in Doc's garage at the start of the movie. In the first few seconds, we get a foreshadowing of things to come....
One of the dials in Doc's garage is a tribute to the CRM-114 featured in Dr. Strangeglove
Doc is wearing the same shirt in 1955 that he wears under his haz-mat suit in 1985