Harsher in Hindsight: The episode "Eva Braun" interviews David Irving, treating him simply as a Talking Head expert on Nazi Germany and World War II. The episode was made back when Irving was still considered a reputable historian. He would later come out as a Holocaust denier. That by itself is bad enough, but what makes it worse is the fact that the show was narrated by a Jewish actor. Adding further salt to the wound, said Jewish actor would later portray Mel Mermelsteinnote a Holocaust survivor who won a lawsuit against a denialist group and in the process had the occurrence of gassings in Auschwitz during the Holocaust declared a legally incontestable fact in the made-for-television film Never Forget.
Nightmare Fuel: The series had a music score that when combined with Nimoy's voice was enough to guarantee nightmares, especially when the episode is about nightmares.
The screaming skull.
The Amityville Horror episode includes several clips from the film. Twice we're treated to the close-up shot of a doll's eyes rolling back and glowing red.
The profile on Carlos the Jackal, to a child in the 1970s watching this show that dealt with ghosts, monsters and the like, the inclusion of this real life cold blooded killer terrorist felt terrifying as a real threat, only mitigated slightly by the footage at the end of commandoes training to fight him.
The loving description of a theoretical 1906-level earthquake in modern Los Angeles in the "Earthquakes" episode.
Sequelitis: An attempt was made to revive the series in 2002 with Mitch Pileggi (known as AD Skinner of the X-Files fame) as the narrator, and it lasted for 8 episodes.