Tears of Fear: Roger Ebert described children in the first theatrical showing were sitting in their seats silently crying in horror.
What's so special in this case is that thanks to movie gimmicks such as those created by William Castle, many horror movies of the '50s and '60s had become the equivalent to carnival fun-houses, good for a harmless thrill and very popular with kids. As a result children growing up at that time went to see Night of the Living Dead expecting spooky fun and instead were genuinely terrified by what they saw, a fact not lost upon Mr. Ebert.
The character Judy wasn't originally in the story. Apparently the actress was just so sweet and photogenic that the crew created a part for her and just made up scenes for her as they went along. Which explains why she's basically a Living Prop.
The car crashing into a tree was done on a whim because they needed an excuse for why there was suddenly a dent in it after getting in an accident during production.
Barbra goes barefoot quickly in the movie because the crew lost one of the shoes. To this day the actress believes it was stolen by a crew member with a foot fetish.
Barbara's description of the events in the cemetery don't match what happened very well. This can be explained in-movie by the fact that she's going a little nuts. It's a little clearer why this is when you learn that that scene was ad-libbed, and the cemetery scene was the last scene filmed anyway.
What Could Have Been: Working titles for the film included actually Night of Anubis and Night of the Flesh Eaters.