The mentally handicapped serve all sorts of functions in real life, but only one in the movies: to inspire callous, self-obsessed adults with their childlike innocence. From Rain Man to I Am Sam to the mawkish new Belgian import Pauline & Paulette, the formula rarely wavers. Act One: The busy schedule of the protagonista lonely, single, egocentric adult, usually a fast-talking, career-driven urbaniteis upended when a retarded person is suddenly foisted upon him or her. Act Two: Amid constant exasperation and occasional public embarrassment, the protagonist's steely resolve is occasionally chipped away by a cute or touching gesture. Act Three: Courtesy of some heartless bureaucracy and/or insensitive lout, the protagonist is overcome with an urge to be protective and nurturing, and, a few teary scenes later, to finally transform into a decent human being. For Pauline & Paulette, writer-director Lieven Debrauwer introduces two astonishing variations on the formula: It's shorter than usual (78 minutes) and it centers on the elderly. Dora van der Groen, a revered actress in Belgian cinema for nearly 50 years, acquits herself well as a sweet, guileless simpleton who lives happily with Julienne De Bruyn, the eldest of her three sisters. When Bruyn dies, the other two sisters are not anxious to care for Groen, but the will stipulates that neither gets a share of the estate unless one assumes custody. Though Groen clings to the scolding Ann Petersen, who busies herself with a small-town fabric shop and sings in a local operetta, she also spends time with Rosemarie Bergmans, a bourgeois city slicker who lives with her arrogant French boyfriend (Idwig Stephane) in Brussels. Banal and patronizing, with a few wild swings at arthouse poeticism, Pauline & Paulette has the courtesy to run through its paces quickly, but only because it doesn't give full weight to the sacrifices involved in caring for the mentally handicapped. Groen's three sisters are as broadly conceived as their décor: The motherly Bruyn's house is ensconced in sensible browns, while Petersen's garish shop is swathed in eye-bursting pink, and Bergmans' city apartment is littered with cold, modern furnishings. With Groen reduced to a winsome deux ex machina, any real complexity has to come from the other sisters and their struggles to integrate her into their busy schedules. But like everything else in Pauline & Paulette (most notably, a series of overwrought montage sequences set to Tchaikovsky's "Swan Lake"), Debrauwer's characterization is as sharp and incisive as a butter knife.