In Germany, Switzerland and Austria, where "The Persuaders" ("Die Zwei") was wildly popular, this series was dubbed in an irreverent way, ad-libing a lot, thus departing from the original scripts and using very funny, often absurd colloquialisms and phrases. (For example the speakers even improvised jokes about their own dubbing work in process). Because of that, in Germany, it had more of a comedy element to it, more so than its original version, making the characters even more quirky and lovable. The German dubbing owes a big part of this show's success and popularity in Germany, Austria and Switzerland. (The same thing happened there with the dubbing for Starsky and Hutch (1975)). Other countries, such as France, would follow the German model. Tony Curtis even asked Rainer Brandt, the German speaker, to write the dialogs for the next season, but the series got canceled before this could have been done.
According to the DVD commentary, neither Roger Moore, an uncredited co-producer, nor Robert S. Baker, the credited producer, ever had a contract other than a handshake with Lew Grade. They produced the entire 24 episodes without a single written word guaranteeing that they would ever be paid.
The most ubiquitous firearm used in the series is a Model 1934 Beretta in 7.65 Browning (aka .32 ACP). It appears in almost every episode involving a handgun. When a revolver shows up, it is almost always a Colt Detective Special.
Throughout the series, Tony Curtis' character Danny Wilde is almost always seen wearing gloves. According to DVD commentary, this was a gimmick developed by Curtis to make his character unusual, and therefore create some buzz for the series.
Popular in Denmark and still repeated on TV 40 years after. The Danish title "De uheldige helte" (The Unlucky Heroes) plays with the words held=luck and helt=hero. The title tune was also a bit of a hit.
In Germany and some other European countries, this series was dubbed in an unconventional way, using very funny, often absurd expressions and phrases. Because of that, it became very popular (unlike the English version) and is still regularly repeated on German TV today.
The filmed sequences presenting Danny Wilde and Brett Sinclair in the opening credits were not filmed expressly for said credits but were taken from various early episodes (all of them in Southern Europe), mainly The Persuaders!: Overture (1971) (the two men racing their sports cars, Tony Curtis and Roger Moore distracted by a blonde in a bikini walking between them, Brett flirting with two beauties) and The Persuaders!: Powerswitch (1971) (the water-skiing shots and Danny shown as a businessman at work at a desk)
Tony Curtis was born Bernard Schwartz of Hungarian immigrants. And if you pay attention, you will find the actor sprinkling inside jokes to his origins through the series. In The Persuaders!: Greensleeves (1971), for instance, his character pretends to be Brett Sinclair's new butler, Grzegorz (Gregor), and explains his (fake) East European accent by his being from a "Hun-GAA-rian" from "BU-dapesht" (unfortunately for Danny Wilde, the black beauty from an African republic that he shares this with speaks the language perfectly). Torn from his Paris hotel shower in The Persuaders!: The Old, the New, and the Deadly (1971) by the telephone ringing which turns out to be a wrong phone number, a dripping wet Danny states, "No, this is not Mr Schwartz, you got the wrong room!"