It was Karl Malden's idea to have his character speak in a different accent constantly. He thought it would be an amusing gimmick.
Unlike the novel, this takes a light-hearted, spoofy style with Dean Martin essentially playing himself. The Matt Helm of the novels is a much darker creation.
Another of Karl Malden's Sekulovich films. Just before he finds out that Matt Helm is still alive, Malden's character refers to Operation Sekulovich. This is his original surname and he often mentioned it in films in which he appeared.
The large, white hovercraft appears to be a Saunders-Roe Nautical 6 (SR.N6). The smaller hovercraft appears to be the Britten-Norman "Cushioncraft" 5 (CC5). There was one CC5 built which capsized during tests off of Priory Bay.