In the glory days of TV's "Saturday Night Live," writers Al Franken and Tom Davis developed a reputation for wit and sharp-edged political satire. ONE MORE SATURDAY NIGHT marked the duo's first venture into screenwriting and undoubtedly will be a disappointment to Franken and Davis fans. This is not the clever parody one might expect, but rather a dimwitted teenage comedy. In a small Minnesota town, local residents are preparing for the biggest social night of the week. The Neals (Dianne B. Shaw and Meshach Taylor) are going out for the evening, unaware of the plans of their babysitter (Nina Siemaszko) and her boy friend (Frank Howard). Meanwhile 15-year-old Doug (Eric Saiet) heists his father's car and goes to see his girl friend (Jessica Schwartz), who has her own wild plans. A middle-aged widower (Chelcie Ross) is preparing for his first date in nearly 20 years, while his teenage daughter (Nan Woods) is having problems of her own with her boy friend (Dave Reynolds). ONE MORE SATURDAY NIGHT suffers from trying to explore a variety of situations, and ultimately gets nothing said at all. The situations are routine, lacking wit or originality. Director Dennis Klein's pacing is slack and reveals no flare for comedy.