The two very famous stars (at the time, in the notorious Frank Sinatra orbit), in their mid- to late-forties, were playing silly "hip" and "mod" types, in a typical late 60s Silly-British-James-Bond-Rip-Off.
Apparently this movie was a sequel to "Salt and Pepper" (which I have not seen), about two nightclub owners Salt (Sammy Davis Jr.) and Pepper (Peter Lawford). It's not as weird as it seems back then, stars were stars even if they were middle-aged. These days if you're over thirty you can't be a lead; but in the good old days of freewheeling movie-making you could be in your fifties and a heart throb.
And this movie is pretty freewheeling, as it was directed by the totally unprofessional Jerry Lewis, Dean Martin's sidekick and most famous these days for telethons and running around yelling, "Lay-dee! Lay-dee!" Jerry Lewis was a megalomaniac of the worst kind, one with no discernible talent. He does a lousy job which was a shame, since Sammy Davis, Jr. had enormous talent. He could sing, dance, act and do voices. He was one of the most talented individuals in the public eye in the twentieth century and it shows through. But mostly, Lewis lets Davis run around with as little discipline as himself.
Everything looks like it might have been put together by amateurs for a college course. The plot is silly, but lots of them were back then. It was a kind of "deconstruction" of movies in the late 60s. Watch Tony Curtis movies like "Arrivederci, Baby!" or Dean Martin's "Matt Helm" flicks (which may have drawn Lewis to this project, as he always liked to play "catch up" with Martin). Silly was in, but this flick was hardly as well done as later with the Abrahams/Zucker or the Farrelly Bros.
Apart from keeping Lawford and and Davis in the public eye and keeping them "cool," I can't think of a reason for making this movie at all. The plot is silly, the acting is on par with people who know they're doing a picture of little value, and Lewis made a hash of the direction. It's one of the movies you watch through just so you'll never have to see it again.
Highlights: 1) Mix-up of the opening credits (you know you're in trouble if that's the best part); 2) a couple of good cameos in unexpected places (okay, if you're in imdb you can see Christopher Lee and Peter Cushing are in it; and though they're only there for a few seconds, they lift the movie momentarily.