Phil Silvers had short-term memory loss during the making of the film and had to have boards placed behind the camera so he could his lines. Kenneth Williams publicly rebuked him both on-set and in his personal diaries for this.
Phil Silvers replaced Sidney James in the role of Sgt. Nocker, which had been originally written for James; it turned out that James could not do the film due to commitments on George and the Dragon (1966). About two weeks into filming that picture James suffered a mild heart attack.
This the second "Carry On" film produced by Rank, and like Carry On... Don't Lose Your Head (1966), it was released without the "Carry On" prefix. Apparently this was done for legal reasons, as Rank had just changed distributors, but the "Carry On" prefix was able to be used again starting with the next film in the series.
Bernard Bresslaw plays a character called Abdul Abulbul. This is a reference to a popular British drinking song (with unprintable lyrics) called Ivan Skavinsky Skavar, in which the eponymous young Russian engages in a sexual duel with the wily Turk Abdul Abulbul Emir.
Some of the film's literal English-language translations of its foreign language titles were "Carry On in the Legion" (USA), "In the Desert, No Water Flows" (West Germany) and "Carry On with the Foreign Legion" (Hungary).
The character named "Corktip" is a parody of "Cigarette" in Under Two Flags (1936), a movie about the French Foreign Legion in the Sahara desert. The name refers to cigarettes, such as the Craven A brand, which had a cork tip.
If the scene where Bo West (Jim Dale) drops the rifle on Commandant Burger's (Kenneth Williams) foot, Dale actually did accidentally drop the rifle onto Williams' foot instead of onto the sand. It was so heavy it cut the boot leather. Williams' painful reaction was real, and he can be seen limping in several subsequent scenes. Dale insisted it was accidental but Williams wrote in his autobiography that he was sure it was deliberate.