Show Business: Silly Songs and Smiling Faces

A new old musical, The Pirates of Penzance, captures Broadway

It is a most improbable hit: a dusty, century-old operetta that nearly everybody has seen—and yawned at—in high school.

But there it is, packing them into Broadway's biggest house night after night and sending them out into the frigid January air with silly smiles on their faces. But then this updated version of Gilbert and Sullivan's The Pirates of Penzance has something few other musicals can boast of: absolute, unqualified, irresistible fun.

The plot is as lovably ridiculous as it always was. There is the...