Monday is Get a Different Name Day. Southern Californians are pros at this. Consider the Los Angeles Angels of Anaheim. Or L.A.'s mayor, at right, who was Antonio Villar until he wed Corina Raigosa. The real connoisseurs were the old studio bosses, who turned Roy Harold Scherer Jr. into Rock Hudson and Gladys Marie Smith into Mary Pickford. To observe the holiday, you could spend the evening with "Romeo and Juliet" and "a rose by any other name." Or, for the epitome of a.k.a., watch "North by Northwest," in which Archibald Alexander Leach plays Cary Grant playing Roger O. Thornhill playing George Kaplan, and looks good in every role.