Tony Musante's hair goes from short to long several times during the film. This is because he keeps taking off the curly wig he is supposed to be wearing as a disguise.
When George C. Scott puts on part of the carburetor at the beginning of the movie, he doesn't add the gasket.
George C. Scott's character is supposed to be half-Portuguese, and he's lived in the country for nine years, yet he pronounces 'Algarve' in a quasi-Spanish fashion: Al-GAR-vay.