The sound of the punchbag in the theme song was made by a drummer beating an old leather attaché case. They couldn't use a recording of a real punchbag because the song was in 4/4 time and a properly-hit punchbag beats in 3/4 time.
One episode took place on a nuclear submarine and the producer wanted the sound of a sub humming in the background. Sound effects editor Robert V. Greene called the Navy who told him that nuclear submarines don't make any noise. Undeterred, he placed a microphone inside an old IBM electric typewriter and recorded the "whir and clicks" it made. The next day the producers loved it and asked where he got it. He told them that some Navy guys in San Diego had sent him a tape.