Who said "Marty, we're running out of time. We must act now."?

This quote is attributed to Doc Brown.

Marty, we're running out of time. We must act now. - Doc Brown

"Marty, we're running out of time. We must act now."

Doc Brown

"This is heavy."

"There's that word again, 'heavy.' Is there something wrong with the Earth's gravitational pull in the future?"

"Great Scott!"

"If my calculations are correct, when this baby hits eighty-eight miles per hour, you're gonna see some serious shit."