This episode opens with Doctor Smith finding a harp under a keyhole shaped doorway, plucking a few strings and suddenly finding himself plummeting into HELL! As the episode progresses we learn its not actually hell but a prison for a very long lived alien named Morbus who just happens to be wearing a flashy red suit. He couldn't have looked any more like the devil if he had a pitch fork in his hand.
The gag however involves the preview to this episode which was attached to the end of the previous episode, the one with Zeno the "superswift". At the end of that episode, Doctor Smith finds the harp, but when he plucks it, it plays the very recognizable tri-tone NnnnBbbbCccc and then Smith finds himself falling into hell. Clearly this was a CBS network jab at NBC and the kind of gag you just don't see on TV any more. Whats even more interesting is that the NBC tri-tone is only heard in the preview, not in this actual episode. I've always wondered why.
The gag however involves the preview to this episode which was attached to the end of the previous episode, the one with Zeno the "superswift". At the end of that episode, Doctor Smith finds the harp, but when he plucks it, it plays the very recognizable tri-tone NnnnBbbbCccc and then Smith finds himself falling into hell. Clearly this was a CBS network jab at NBC and the kind of gag you just don't see on TV any more. Whats even more interesting is that the NBC tri-tone is only heard in the preview, not in this actual episode. I've always wondered why.