A.J. Quartermaine is a fictional character from General Hospital, an American soap opera on the ABC network. Born on-screen in 1979 as the only biological child of the iconic Drs Alan and Monica Quartermaine, A.J. was SORASed in 1991, revising his birth year to 1972. The role has been most notably portrayed by actors Sean Kanan from 1993 to 1997, and Billy Warlock from 1997 to 2003, with a brief return in 2005. Kanan made his on-screen return as A.J. on October 26, 2012, after a 15-year absence.

The newborn A.J. was portrayed by child actor Eric Kroh from 1979 to 1983. Abraham Geary briefly stepped into the role in 1983. The role was also portrayed by Jason Marsden (1986-1988), Christopher Nelson (1988), Justin Whalin (April 1988 - 1989). On June 20, 1991, Gerald Hopkins stepped in the role of A.J. on contract and last appeared on December 30, 1992. The role was recast with Sean Kanan, who made his first appearance in the role on February 16, 1993. Kanan last appeared in the role on June 10, 1997. Kanan received a nomination for the Soap Opera Digest Award for Best Newcomer for his portrayal of A.J. in 1994.  Following Kanan's departure, actor Billy Warlock was hired for the role of A.J., and he made his debut on June 13, 1997. In 2003, Warlock earned a pre-nomination for the Daytime Emmy Award for Outstanding Supporting Actor in a Drama Series for his portrayal of A.J.. Warlock departed from the series in December 2003, amongst rumors that he was fired after disputes with show executives; the network replied his exit was due to lack of storyline.  In early 2005, the network's announcement of Warlock's return as A.J. was briefly put on hold, speculated as contract disputes. Warlock's return first aired on February 4, 2005, and shortly thereafter Warlock announced his return to the NBC soap opera Days of Our Lives as Frankie Brady. Warlock's exit lead to rumors of Kanan's possible reprisal of the role, who had recently announced move to recurring status in his role as Deacon Sharpe in the CBS Daytime soap opera The Bold and the Beautiful. Warlock exited the series in April 2005 and the character was killed off.  On September 17, 2012, Kanan revealed in an interview with TV Guide's Michael Logan that he was put on contract with General Hospital, but his character was not being announced. Rumors arose that Kanan might replace Steve Burton in the role of A.J.'s brother, Jason Morgan; the resemblance between the two fed into the rumors. Kanan first appeared on October 26, revealed to be A.J., retconing the character's death. On March 17, 2014, it was announced that Kanan would once again be leaving the role of A.J.Answer this question using a quote from the following article:

What other actors played this role?
Jason Marsden (1986-1988), Christopher Nelson (1988), Justin Whalin (April 1988 - 1989). On June 20, 1991, Gerald Hopkins stepped in