With the storm clouds of revolution apparently gathering just beyond their gates, and the doldrums of decorum weighing heavily on their souls, a fictional British royal family goes slumming among life-loving commoners and comes home feeling inspired. This 1935 divertissement, conceived by playwright Moss Hart and composer-lyricist Cole Porter while on a five-month luxury cruise with their famous friends, is the show that 42nd Street Moon started up with in 1993, revisited to much acclaim in 1997, and has very winningly brought out once again. If this Eureka Theatre production doesn't affirm the endurance of Depression-era musical farce, nothing will. Director Greg MacKellan gives his committed cast — including Megan Cavanagh, Michael Patrick Gaffney, Juliet Heller, and Andrew Willis-Woodward as the wayward royals — some fun bits of business to play with, and Tom Segal's ambitious choreography goes well beyond mere jutting elbows and jazz hands. If you're someone who still hopes for a good Porter-Hart musical, it's just what you'd hope: swift and fizzy and quippy and quite fun to be with.