Hunger, like all urgent and uncontrollable bodily functions, is an eternal wellspring of humor. Think of Charlie Chaplin grimly carving up his boot in The Gold Rush, Mr. Creosote’s last supper and that old, reliable sight gag, the fellow desert-islander who morphs into a talking turkey leg. Tummy rumbles equal belly laughs, and both abound in the National Theatre’s gobsmackingly funny One Man, Two Guvnors. Driven in its first half by the peckish desperation of freelance flunky Francis Henshall (James Corden), this virtuoso banquet of slapstick farce and verbal jousting brings with it a shocking revelation: How starved we were for comedy.