“Frankie & Johnny” is a hard movie to dislike. Marshall and McNally have a real fondness for their characters and a deep trunkful of showbiz savvy. The playwright’s delicious one-liners detonate with precision timing. The supporting characters, expertly played, have the kind of instant familiarity of regulars on a favorite TV sitcom. There’s Kate Nelligan, delightfully cast against type as the brassy, sexually aggressive waitress, Cora; comedian Jane Morris as the sour wallflower Nedda; Nathan Lane as Frankie’s witty gay neighbor and confidant (who gets the best zingers), and Hector Elizondo as the diner’s watchful Greek owner.

People who saw Kathy Bates and Kenneth Welsh on stage scoffed at the idea of casting Pfeiffer and Pacino in these unglamorous roles. It’s true that Pfeiffer can’t disguise her beauty, for all her efforts to look as haggard as possible. But her performance blows this quibble away. Frankie is a woman with good reasons to fear involvement, and Pfeiffer isn’t afraid to expose her most vulnerable emotions. You’re convinced she’d rather curl up at night with ice cream and a videotape than risk loving again. Pacino is a good romantic partner and lord knows he’s winning as the extroverted, extravagantly optimistic Johnny. Maybe too winning: Pacino’s eager-to-please performance accentuates the too-good-to-be-true nature of the role. Where’s this guy’s buried layer of fear and frustration? Without that edge of reality, “Frankie & Johnny” becomes another fairy tale about a white knight who rescues a maiden from her emotional fortress.

It’s not Pacino’s fault that the movie is easier to enjoy than to believe. The filmmakers seem to confuse cinema shtik with real life: their view of working stiffs owes more to Hollywood than Hell’s Kitchen. “Frankie & Johnny” is a lot of fun when it aims to charm; when it asks to be taken seriously as a realistic look at urban romance, it seems as evanescent as television airwaves.