It’s not every season that weary fashion types stomp their feet and cheer like teeny boppers during a show. But that’s just what happened when Prince started singing – quietly at first – from his front-row seat before the start of Matthew Williamson’s show on Wednesday. He then hopped up on stage, where a small band had been assembled, strapped on his guitar, and started to croon “Chelsea Rodgers” as Maya and Nandy McClean – aka the Twinz – grooved beside him. As he played, the girls sashayed down the runway with the real Chelsea Rodgers – a model in the Williamson show and muse of Prince’s – as the audience watched and cheered. The performance was a 10th anniversary present to Williamson, his business partner Joseph Velosa said.