Dark Shadows nearly ended after a weak start on ABC in 1966. Creator Dan Curtis introduced a vampire character to boost ratings.
The daytime drama followed a governess at the Collinwood estate in Maine. It featured limited supernatural elements at first.
ABC threatened to cancel the show unless viewership improved within 26 weeks. Head writer Sam Hall recalled the network's ultimatum.
Curtis added Barnabas Collins, played by Jonathan Frid, who debuted in April 1967. The vampire had been trapped in a coffin since 1795. The change turned the series into a sensation.
Frid gained widespread fame similar to the Beatles. The show produced 1,225 episodes over five years before ending in April 1971.