Prince treated fans to a surprise last night during his performance at Los Angeles’ Forum, where he’s currently on a 21-night concert run. The Purple One brought out Alicia Keys to duet on his hit “How Come U Don’t Call Me Anymore?” which she later covered for her 2001 debut songs in A minor. During the rendition, the pop icon manned the piano while Ms. Keys stood by his side, complimenting his vocals with her smooth trills.