Audio problem: Magnum slips into the car in 1936 with his client out of the club. If you pay attention to the audio, there is sometimes a droning noise as if someone were using a leaf blower nearby (it's actually because in editing they cut out all sounds below a certain level - but some of it spiked enough to stay into the audible range). (00:11:20)
Magnum, P.I. (1980)
1 audio problem in Flashback
Starring: Tom Selleck, Roger E. Mosley, John Hillerman, Larry Manetti
Other mistake: With power out Magnum somehow lights the gas stove with the knob, which is electric. Should have used a match. (00:26:40)
Higgins: How fiendishly deceptive of you, Magnum. I could have sworn I was hearing the emasculation of a large rodent. To my great surprise, I see the sounds are emanating from what I thought was a harmless musical instrument.
Magnum: Cute Higgins, real cute.
Higgins: Why Magnum? Why do this terrible thing?
Magnum: Higgins, I'll have you know I used to be very good. I was the second best sax player in my High School band!
Higgins: Well, how many sax players were there?!
Magnum: ...Anyway. I just saw this in a pawn shop window and thought I'd like to try and get my chops back.
Higgins: May I suggest that your "chops" are irretrievable.
Magnum: Higgins, did you come here just to abuse me!? (00:05:25)
Trivia: Tom Selleck is the only actor to appear in every episode of the show.