There are countless examples of movies that can't decide what they want to be, and, as other users have pointed out, this is one of them. It's personality is split three ways - a comedy, a romance, and a social commentary sermon. By not committing itself fully to any one of these, it fails at all three. As a comedy it is unquestionably the most leaden one I have ever seen. The humor is forced, and none of the dialogue has any wit or sparkle. Prepare for vast stretches of confusing pointlessness. As a romance, the interaction between the two protagonists is totally unconvincing. And as far as social commentary - the aspect we can doubtless attribute to the socialist George Bernard Shaw, upon whose play it is based - it has all the subtlety of a polo mallet upside the head. The two greats, Alastair Sim and Peter Sellers, do as best as they can with what they are given. Sellers in particular does well reprising the Indian persona he perfected on The Goon Show. But Sophia Loren seems to have been chosen purely to flaunt her sex appeal which, though considerable, poses obvious and clumsy distractions from the story, and her character is totally unbelievable as far as motivation or personality. The movie is a complete waste of the talents of the actors involved.
Review of The Millionairess
