Many lines from the trilogy make us laugh. However, Doc Brown actually gives us these two gems that we can all apply to our lives.

From the first movie it's this: If you put your mind to it, you can accomplish anything.

Interestingly enough, while that proverb is attributed to Doc Brown - he never actually says that on-screen.

From the end of the trilogy: Your future is whatever you make it, so make it a good one!

I thought it was a great way to end the trilogy with that line. :)

"If you put your mind to it, you can accomplish anything."

George says it too.

Only because Doc said it first, then Marty went back in time and said it to George. It's funny how that works. George probably thought it was a coincidence that he and Doc were both saying that - but Doc probably figured out that it wasn't such a coincidence, and that it was likely that Marty told George about it.

Then again, if Doc wasn't already saying it back in 1955 - I think he did, as he teaches third grade students in my fanfic universe - and Doc was influenced by George to start using that proverb, then you have some sort of a predestination paradox.

It'd be so weird:

1. TP Doc -> Marty
2. Marty -> George
3. George -> LP Doc

It'd be even weirder if Marty himself influenced Doc to say that proverb in 1955. Then again, he also would have in the above example - albeit indirectly.