She's a Man, Baby, a Man! - S2.E5

The sisters discover that Phoebe is psychically linked, through her powers, to a man-killing demon known as a 'Succubus.' In order to lure the Succubus to the sisters, Prue casts a spell, which turns her into a man. Meanwhile, Piper discovers from a video tape at the dating service that their new neighbour, Dan, is interested in her.