Lacey is Vanessa's friend whom only been mentioned when Vanessa was on the phone with her in "Hail Doofania!." Not much is known about her, though since the episode involved Vanessa acting like Candace, her name is likely meant to be a play on "Stacy," Candace's best friend (whom she often talks on the phone with). It has been said at the San Diego Comic Con in 2009 that she is the equivalent of Stacy for Vanessa.
