Michael Palin's father stuttered, so Michael used a lot his real life experience when playing Ken, including the fact that Ken's stutter is less pronounced around people he trusts (Tom and Wanda) and worse around people he is uncomfortable with (Otto).
In 1989, when this film was shown in the theaters in Denmark, a Danish man named Ole Bentzen, a Danish audiologist, literally laughed himself to death during the scene where Ken gets the chips up his nose. Bentzen's heart rate went between 250-500 beats per minute and he eventually succumbed to cardiac arrest. The story behind this is that the man had made a joke a few years earlier with his family during dinner, where he put a piece of cauliflower up his and every family members nose as a joke and made a bet with them on who could eat up their carrots without the cauliflower falling out. When the scene with Ken and the chips came up, he started thinking about this dinner-incident and laughed so hard that his heart stopped. This story is well known in Scandinavia and spread around as almost an "urban legend" shortly after it happened. It was confirmed by his son, who also told the dinner-story as an explanation to why his father laughed so hard during the chips-scene that he died.
Archie speaks in Italian: "Ma ho sposato una donna che preferisce lavorare in giardino a fare l'amore appassionato. Uno sbaglio grande!", what translates as: "But I married a woman who prefers working in the garden to making passionate love. A big mistake!". It can actually refer to Archie's marriage.
When Otto leaves Archie's home, he says to Archie's wife Wendy that they would all speak German without the USA. He leaves the house while singing the first verse of the anthem: "Deutschland über alles". The German dubbed version has an altered dialog, he says that they'd all eat sauerkraut and listen to military marches, then he imitates some military marches instead of singing the anthem, as the first verse is considered too nationalist and generally not sung in public.
During the love scene, when Wanda opens up her blouse, Otto says in broken Italian "Ecco le due cupole del catedrale di Milano!" which translates "There are the two domes of the Milan cathedral." Milan's cathedral, actually, has no domes at all.
Kevin Kline begged John Cleese to let Otto speak French instead of Italian when he wants to seduce Jamie Lee Curtis, since Kline speaks French. Cleese insisted that it had to be Italian. Kline started singing "Volare" because he ran out of Italian cheeses and other Italian phrases that he could ad lib, and was concerned that the director did not yell cut, since the producers did not own the rights to "Volare" when the scene was being filmed.
John Cleese claims that this is Charles Crichton's movie. He merely took a co-director credit to reassure studio execs who were worried about Crichton's advanced age and the fact that he had not directed a theatrical movie for 23 years. The only work major work Cleese did as director was near the end of the shoot, when he handled various scenes mostly involving Michael Palin, to allow Crichton to start overseeing the editing.
For the French dubbed version when Wanda states that Otto mistook the Gettysburg Address for Lincoln's residence, it is replaced with Wanda stating that Otto mistook General Motors for a hero of the war of '14.
John Cleese chose the name Archie Leach, Cary Grant's real name, because he was born 20 miles away from where Grant was born (Hughenden Road, Horfield, Bristol), and because it was the closest Cleese could get to being Grant.
In the opening sequence that introduces the principal cast, a model of the Eiffel Tower can be seen over Michael Palin's shoulder. This may be a reference to Charles Crichton's earlier film The Lavender Hill Mob (1951), in which Alec Guinness tries to smuggle the stolen gold out of England by melting the gold down and disguising the stolen gold as a model of the Eiffel Tower.
The British Airways plane that can be seen at the airport is a Boeing 747-236 called "City of Manchester", registration G-BDXC. It was sold to European Skybus Ltd & scrapped in 2002 after about 25 years of service.
The dog death scenes were originally filmed with entrails from a butchers scattered around the dead dog. Preview audiences reacted strongly to this, so the scenes were reshot with an obviously fake straw dog.