What do a clown and a ballerina have in common? Plenty, as it turns out, if, that is, the clown is none other than the masterful Bill Irwin and the terpsichore is New York City Ballet principal Tiler Peck, curator of BalletNOW, a trademarked, quasi-gala that features leading dancers from New York City Ballet, American Ballet Theatre, Miami City Ballet, the Royal Ballet and Paris Opera Ballet in three diverse, tasting-menu type programs.