The fourth season of Family Guy aired on Fox from May 1, 2005, to May 21, 2006, and consists of thirty episodes, making it the longest season to date. The first half of the season is included within the volume 3 DVD box set, which released on November 29, 2005, and the second half within the volume 4 DVD box set, which released on November 14, 2006. Volume 4 is split into seasons 4 and 5 in region... Wikipedia