I'm fond of the Back to the Future theory that Doc knew Marty died when Biff was about to run him down in his car at the end of the tunnel in the second movie. Doc drops the flag rope at the last possible second, but there's no way he could've known to do that unless Marty got hit and died the first time which prompted Doc to use the Delorean to jump back to before that happened in order to use that knowledge to save him.
16 BEST MOVIE THEORY EVER
22 YOU ARE NOW THE MANAGER OF PURGATORY ITS A MIX BETWEEN HEAVEN AND HELL HOW WOULD YOU MAKE PEOPLE ...
31 WORST THING YOU HAVE DONE BECAUSE YOU GOT CONFUSED BETWEEN ITEMS IN DIFFERENT HANDS
17 A TV SERIES THAT EVERYONE SHOULD GIVE A GO
19 YOUR FAVORITE KIDS MOVIE IS NOW RATED PG13 AND IS ALLOWED A SINGLE FBOMB WHERE DO YOU PUT IT
24 ORS WHO ARE CLEARLY NOT THE FAVORITE CHILD HOW DID THAT AFFECT YOU
17 YOU'RE TELEPORTED BACK IN TIME TO YEAR 1821 IN THE SAME EXACT PLACE AS YOU'RE NOW OR GROUND LEVEL...
26 SLOWLY GAINING POPULARITY THAT MOST PEOPLE DON'T KNOW ABOUT YET
30 WHAT MADE THE WEIRD KID AT YOUR SCHOOL WEIRD