After a fantasylike day repeatedly encountering the same woman, including as a mannequin in a store window, a young man finally gets to lock lips with her on-screen at a drive-in movie, in a spot that broke last week for Scope. The 45-second commercial is Procter & Gamble Co.'s first cinema ad for the mouthwash, and it also will run nationally on TV in :45 and :30 versions. Dubbed "Saturday Night," it is the latest in Scope's "Tingle" campaign. D'Arcy Masius Benton & Bowles, New York, handles. Copywriter: Palmer Davis. Art director: Michelina Pagano.