Even the invitations were cryptic. Printed on shocking-pink paper, they read, "Please come to Madonna and Sean Penn's birthday party Aug. 16. Please be prompt or you'll miss the wedding." Those on the select mailing list understood the reference: the bride would turn 27 on her wedding day, and the bridegroom 25 the day after. The card instructed guests to phone a special number to find out where the supersecret event would take place. Not even the chic caterers knew where to deliver their delights (pizza and curried oysters, Madonna's culinary favorites) until the very last minute.
Yet despite all the...