I'm fascinated by what came before SHOCK! in the 1950s--what primed audiences to accept into their hearts and nightmares old Universal horror and mystery films when the SHOCK! package made its television debut in October, 1957.
This is a time-line, updated at times, of important horror film events that came before SHOCK!
Pre-1950s - 1950s: Spook Shows. One never hears of their influence upon the monster craze of the late 1950s, but surely spook shows, typically hosted by a magician, were the horror film host events of their time, drawing in packs of young people in theaters across the United States. Even Bela Lugosi had his own spook shows during this time. Perhaps not unexpectedly, spook shows began to die down as more and more monster fans sat home watching horror hosts and horror films on television.
1954 (April 30) - 1955 (April 2): THE VAMPIRA SHOW, airing on KABC-TV from Los Angeles. Soon after its premiere, major news magazines like LIFE and NEWSWEEK contained features on the show and its star, Maila Nurmi. TV GUIDE also devoted an article on the show. THE VAMPIRA SHOW appears to be the first horror hosted film show on television. 50 episodes were shown, with the films being of the public domain variety, like REVENGE OF THE ZOMBIES, THE DEVIL BAT'S DAUGHTER, and FOG ISLAND. In the SHOCK! promotional book, a suggestion was made to have that package hosted by horror hosts.
1956: THE VAMPIRA SHOW is revived on another Los Angeles station, KHJ-TV.
1956 (May): A television showing of KING KONG in the NY City area was watched by about 90% of people with television sets, an extraordinary feat. This event may have been the prime influence for Screen Gems to get together their SHOCK! package.
1957 (June 19): I WAS A TEENAGE WEREWOLF premieres, double-billed with INVASION OF THE SAUCER-MEN. The film will become a huge hit, one of the ten top grossing films of 1957. It's unlikely that the film had a chance to influence the release of the SHOCK!, considering that only four months separated the two events, but it certainly may have prepared audiences for the SHOCK! television package.
1957 (June 25): A week after the premier of the above, Hammer Films' CURSE OF FRANKENSTEIN makes its first USA showing. It also is a significant success.