"My PDA right here now has a perfect image of you in it. I have a pretty good holo-disguise, too. It's not predetermined that you arrive at the beach last Saturday. Realistically, I could go back disguised as you; it'd be indistinguishable to the me from back then, wouldn't it?"
— Kyon, Kyon: Big Damn Hero
"Sometime today, old Biff will show up to give young Biff the Almanac. Above all, you must not interfere with that event. We must let old Biff believe he succeeded, so that he'll leave 1955 and bring the DeLorean back to the future."
—Doc Brown, Back to the Future Part II
