Doing It for the Art / Executive Meddling: Boris Karloff was attached to the movie because he owed the ever-frugal producer Roger Corman two days' worth of filming. The actor, despite his age and frail health, was so impressed with the resulting script that he volunteered the extra few days of filming needed to complete his part of the project.
Mike Farrell, the guy caught in the Phone Booth, went on to play B.J. Hunnicutt in Mash.
I Am Not Spock: Orlock is Karloff with the serial numbers lightly sanded off. Almost counts as an As Himself trope, although in Real Life Karloff wasn't about to retire, and seemed happy to make this film.