Revealing mistake: When TC and the kids are watching the game live at the stadium, the film is much grainier making excessively obvious the usage of stock footage. (00:17:00)
Factual error: In the flashback of 6 years-old Magnum paddling with his dad before he leaves for the war in Korea, Mr. Magnum is wearing a Rolex GMT Master with the Pepsi bezel, a model designed in 1955, well after the war. (00:12:05)
Continuity mistake: TC is driving his team of youngsters for the 4th of July game; in the aerial shot of the van, it is driving a different road than the one shown in the interior view, and it's driving on the leftmost lane while it had cars on both sides of it and the right railing has been closer. (00:08:00)
Revealing mistake: When Carol and Magnum jump from the terrace, you can see her land way too close to the edge of the garbage truck container; the stuntwoman's foot hits it in fact, and one of her shoes ricochets in the air. The stuntwoman picked up an injury, obviously, but Carol is unscathed and complains just about the suit getting dirty - when at the very least she lost one shoe. (00:25:30)
The Case of the Red-Faced Thespian - S4-E12
Plot hole: The plot of the episode has a big reveal that tricks the viewer making zero sense; the victim is alive and well, but there's an ambulance, they bring the victim away, and Magnum spends most of the episode in the noble effort of saving Higgins from a murder accusation. Magnum mentions "I figured I still had about a half an hour before Tanaka returned with a warrant for Higgins' arrest." even in his internal monologue, so it's not that he was trying to hide the fact from other characters.
The Case of the Red-Faced Thespian - S4-E12
Continuity mistake: Trying to exterminate the mongooses with extreme prejudice, Higgins lights up the bombs twice in two separate shots. (00:03:35)
The Case of the Red-Faced Thespian - S4-E12
Continuity mistake: Higgins mentions Robin's project to finance "a home for incorrigible boys." He already has in hand the two bombs he reaches for in the bag during the next shot. (00:03:10)
Other mistake: When Magnum is watching the game on TV, it is also the game TC is watching, which makes sense. What makes less sense is that it is also the same game, same action, that was shown just 3 episodes earlier in 4-8, when Rick and Higgins called him as he was supposedly in the Tiger Stadium with an invite for the locker rooms after. (00:17:35 - 00:34:40)
Other mistake: Rick is telling Magnum about the time he was playing stickball in Chicago. His tale is interrupted by a ball flying high for the home run. The shot, with the ball ending over the outfield fence as it falls, is a blatant recycle from the very opening of the episode; the ball that Danny was pretending to try and catch as he ran to the fence dropped from the sky with those exact same 3 utility poles, in "Taiwan." It's also a clear sky that does not match the overcast sky of the practice match. (00:02:20 - 00:24:20)
Other mistake: Forgetting the absurdity of a kid who's never been on a horse before that can just hop on one and gallop all night long, the stuntman riding Agatha's horse when Higgins and Magnum watch them fade into the night wears a striped shirt; Benny in the morning is still on the horse, on the run, but has a sports jersey with a very different color pattern, basically bi-color with the full bottom half powder blue. (00:36:50 - 00:38:15)
Continuity mistake: When TC asks Benny (of course with no foreshadowing at all) "You don't wanna be someone else, do ya?" his van is parked in front of a hedge. Cut, and they are in front of garage doors. (00:32:45)
Other mistake: In the shots from inside the van it's easy to tell that Benny throws the newspapers in such a weak way that they hardly can reach past the outer fencing and walls - in fact the last one he throws before TC tells him "Not like that" is shown in the next shot landing on somebody's lawn, but from the van window you could see he tossed it into a driveway, at a height that could never go past the hedge. (00:32:00)
Continuity mistake: John Saxon hands Prince Danny's pic to the arcade manager holding it by the top left corner in close-up, but his fingers were on the top right in the wider angle. (00:41:20)
Continuity mistake: Magnum met the Prince 5 seconds earlier and already he has enough of him and says bye, about to drive off. Danny says "Hey", and at the cut the glove rolled from under the right to the left hand. (00:08:20)
Continuity mistake: Rick gets the odds from Magnum and then puts the car in reverse. His left hand is on the left part of the wheel, right hand at the cut. (00:07:25)
Operation: Silent Night - S4-E10
Other mistake: Higgins ask for the hacksaw from TC's toolbox. In 30 seconds sharp (no pauses in the dialogue), Rick brings it to him. So the wrecked airplane and the chopper are 10 seconds apart, in a thick forest. That's quite a bit uncanny. (00:24:15 - 00:24:45)
Operation: Silent Night - S4-E10
Continuity mistake: When Rick says that the place is spooky and reminds him of 'Nam, the pieces of wood he's holding change place entirely (one was under his armpit, now it's across his chest) between shots. (00:13:45)
Operation: Silent Night - S4-E10
Continuity mistake: When TC is lashing out at Rick for the unwarranted comment about "crashing" the chopper, Rick is casting a shadow on him under the closer angle, does not when the camera is positioned in front of Higgins weaving the basket. (00:11:40)
Operation: Silent Night - S4-E10
Continuity mistake: When TC shouts at Higgins for being pedantic about Ukulele Lady, he's holding at different height the piece of equipment he's repairing. (00:11:05)
Operation: Silent Night - S4-E10
Character mistake: Higgins hearing the drunk sailor sing "Ukulele Lady" pitches in saying "Written in 1925 by Gus Kahn, Richard Whiting and Irving Berlin." The song was written by Kahn and Whiting only, who published it through Irving Berlin's eponymous record label. (00:10:50)