The Music Box Theatre is promoting this weekend’s revival of The Telephone Book as a guilty pleasure (“Mr. Skin presents!” the website boasts), though this 1971 underground comedy is not nearly as dirty as you might be led to believe. True, the film received an X rating upon its initial release, and most of its characters are self-proclaimed perverts. Yet the humor is cartoonish and surprisingly genial—and so is the lead actress, a wide-eyed, squeaky-voiced belle named Sarah Kennedy. (Too bad she disappeared from movies after the 70s: between this and Stephanie Rothman’s The Working Girls, she proved herself a gifted comic actress.) The closest points of reference might be the Robert Downey Sr. comedies Putney Swope and Greaser’s Palace, which were made around the same time and project the same irreverent silliness.