I spent about half of this whiteface comedy shaking my head in dismay, and the other half throwing it back to laugh. During a society blowout in the Hamptons, two bumbling FBI agents (Shawn and Marlon Wayans) don grotesque prosthetics and body paint to impersonate white debutante sisters who are menaced by kidnappers. The story, concocted by the two stars and big brother Keenen Ivory Wayans (Scary Movie, I’m Gonna Git You Sucka), doesn’t make a lick of sense, and its borderline racism and sexism will offend plenty of people. But comedy is all salesmanship, and these guys sold me; their giddiness reminds me of kids competing to crack each other up at bedtime after mom has given them Pepsi with dinner. PG-13, 109 min.