User blog:The Music Master/Justice League United: Series

Justice League United (Season 1):
During the season, Steel/Natasha Irons, Guardian/Jim Harper, Superman/Kal-El/Clark Kent & John Henry Irons will join the League.

Justice League United (Season 2):
Miss Martian/M'gann M'orzz/Megan Morse would've joined the League.

Justice League United (Season 3):
Agent Liberty/Ben Lockwood would've joined the League.

Justice League United (Season 4):
Red Tornado/John Smith would've joined the League.