This is actually my favorite Peter Sellers film, and my favorite Neil Simon script, though I suppose I'm in the minority there. I just love it to pieces, though, and re-watch it at least once a year. Sellers as thief in prison, as devoted son and stern brother, as American tourist, and especially as a Felliniesque film director--it's just terrific stuff, he is so pricelessly funny, and yet there is somehow a little less of him and more of a script than there is in the Blake Edwards films, which is why I think I like it better. And I do think Victor Mature is marvelous in it too, with a touching wistfulness underneath all the vain posturing. Ditto the chief of police. The sets are fabulous too, and so is the Bacharach music, much of it deliciously cheerfully Italianate but also the wonderfully catchy main title sung by Sellers himself with the Hollies (that would be Graham Nash later of Crosby, Stills and Nash).
There are certain things about the film that remind me of The Producers, though the comedy style is not quite the same. But anyway, not to be missed!