Who said "If I had more guts, I'd go back and push Biff into a lake."?

This quote is attributed to George McFly.

If I had more guts, I'd go back and push Biff into a lake. - George McFly

"If I had more guts, I'd go back and push Biff into a lake."

George McFly Humor

"I'm your density. I mean, your destiny."

"This is heavy."

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

"I'm not very good at science."

"Never underestimate the power of a good laugh."

"Laughter is the best medicine."

"A good laugh is the best medicine."

"Laughter is contagious and wonderful."