Parades, music, dancing in the streets — joyous Carnival celebrations marking the final days of revelry before Lent are peaking in New Orleans, Rio de Janeiro and other locales in the Americas and Europe. Each city has its unique Carnival customs but the similarities are inescapable. Dancers in feathered headdresses gyrated and strutted in parades featuring lavish floats with giant figures of Greek gods or pop stars. Costumes abounded and the themes of the various festivities ran from whimsical to satirical. Shoulder-to-shoulder crowds savored the music and rhythms around a music truck in Salvador or outside Bourbon Street nightclubs in...