Jack's Mannequin is the solo project of Andrew McMahon who is also the vocalist, pianist and main songwriter of the band Something Corporate. 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 the first time ever when he received the call from his doctor.