Better on DVD: Specifically Discotek Media's DVD release. Being able to watch and compare all four English dubs produced for the movie over the years (as well as the Japanese version with subtitles) makes for a rather fun experience.
Internet Backdraft: The misattribution of the old Toho dub to New York-based Peter Fernandez and Friends has been labelled as vandalism by numerous fans, never mind that the one who added the information was genuinely clueless about who did the dub due to a lack of sources regarding the dub (thus, it's actually more like speculation than actual vandalism) and could not have known that the dub was produced by a different group, which was based in Japan.
Moral Event Horizon: Crossed by Starky when he mentions that everyone involved in the operation against Mamo will be eliminated as soon as the operation is complete. What drives it home is his statement on Gordon's fate. As the Streamline dub translates it: "Agent Gordon? He'll be no exception."
So Bad, It's Good: The 1979 Toho dub, though it's still listenable and decent for an English dub produced in the 70's.
The Manga UK dub counts as this. It's mostly well-acted, but Lupin's Dub Name Change and writing tweaks that subtly change Fujiko's motivation land it here.
The Pioneer/Geneon dub using the "Red Jacket" cast counts… for those who have a low tolerance for gag dubs. Otherwise it's just plain good. Not even critics of that cast (most prominently Big Name Fan Reed Nelson, who wrote the liner notes for the Discotek release and slipped in some jabs against it – not the first time he's done that either) can deny that the voice acting is excellent.
Superlative Dubbing: For all its faults and sporadic rewrites, the Streamline dub at least tries to be more faithful to the original Japanese than did their earlier dub of The Castle of Cagliostro. Plus, the scene between Lupin and Fujiko in Paris is hilarious.
The Pioneer/Geneon dub oftentimes doesn't even try to adhere to the subtitles, although the gist and spirit of a scene is usually retained. Despite that (or because of it), it manages to sound even more natural and believable than the Streamline dub. Helps that the cast had been working on "Red Jacket" for at least a few months at that point.
What an Idiot: Mamo tried to blackmail the United States of America. Who have a well earned reputation for blowing up everyone who tries. Guess what the Americans did to his hideout when they tracked it down?