On June 5, 1950, ABC revived "The Adventures of Superman" as a twice-weekly afternoon half-hour series. This version reused the scripts for the 60 MBS half-hour episodes and the 13 "adult" ABC episodes but with new cast members. Michael Fitzmaurice replaced Collyer as Kent/Superman, Jack Grimes replaced Jackie Kelk as Jimmy Olsen, and Ross Martin replaced Jackson Beck as narrator. A total of 78 episodes were produced, with the final broadcast, "The Mystery of the Prehistoric Monster," on March 1, 1951. By then, producer Robert Maxwell was actively preparing "Adventures of Superman" for television.