Related Information for Jack's Mannequin Jack’s Mannequin started off as a side-project of Andrew McMahon, who is the vocalist, pianist and main songwriter of the band Something Corporate but has now become his main project. The band is based in Orange County, California. The name Jack’s Mannequin originated from one of McMahon’s songs called Dear Jack, which was written about a friend of his whose brother was diagnosed with childhood leukemia. Andrew himself was diagnosed with leukemia on June 1, 2005 and cancelled a show for th.. read more