- Both times that Doc gets shot in Part I. Marty's reaction might be a little Narmy to some, but...imagine seeing your best friend killed in cold blood, twice, and not being able to do a damn thing about it in either case.
- And the second time, Marty's reaction to thinking that Doc is dead is heartbreaking. He just slumps back on the pavement and cries. He then looks up with an expression that screams "What am I going to do?" (not knowing, of course, that Doc is alive and sat up behind him).
- It's subtle, but after the skateboard scene where Biff and his goons chase down Marty, he heads back to Doc's lab... and finds that he made it to the end of the 1985 tape.
Doc: (on tape) Oh my god... They found me. I don't know how, but they found me... RUN FOR IT MARTY! (tape rewinds) Oh my god... They found me. I don't know how, but they found me... RUN FOR IT MARTY! (tape rewinds)
- The scene when Biff corners Marty, and finds Lorraine in the car... At that point Marty sums up Biff's character in two simple words.
Marty: Leave her alone, you bastard!
Lorraine: (tearfully) George, help me! Please!
- And when George finds Biff with her instead of Marty, the fact that she sounds so terrified.
- The moment where Marty starts fading away and George looks like he's about to give up on Lorraine after a Jerkass steals her away during the dance, and Marty weakly, inaudibly pleads to George not to do so as he starts to collapse. It's less than a minute, but the intensity of that moment makes it feel so much longer.
- Marty hugging Doc goodbye before trying to get back to 1985. Now more than ever, his mind is on whether his friend will get the message. If he doesn't, this will be the last time he'll see him alive, and Marty knows it.
Doc: In about 30 years?Marty: (briefly looks like he's about to cry) ...I hope so.
- And Marty can't even give Doc a proper goodbye, in case it really is the last time he'll see his friend alive, since Doc steadfastly refuses to listen to anything Marty has to say about Doc's future!