[1] His father, John O'Sullivan, a Toronto native, played for the minor-league Winston-Salem Thunderbirds of the Atlantic Coast Hockey League.

[2] The abuse continued up to the time he started playing for the Mississauga Ice Dogs of the Ontario Hockey League (OHL).

[4] O'Sullivan later detailed the abuse in a book, Breaking Away: A Harrowing True Story of Resilience, Courage and Triumph.

During the 2006 NHL Entry Draft, O'Sullivan was traded (along with their 17th overall pick, eventually used to select Trevor Lewis) to the Los Angeles Kings in exchange for Pavol Demitra.

O'Sullivan, along with Halpern, Jamie Fritsch, Jared Ross, Blake Geoffrion and Jarred Tinordi, are the only NHL players to date to come from the region.

[citation needed] On November 2, 2006, O'Sullivan was assigned to the Kings' AHL affiliate at the time, the Manchester Monarchs.

Unable to earn a regular position, scoring 4 points in 23 games to begin the 2011–12 season, O'Sullivan was reassigned to the Coyotes' AHL affiliate, the Portland Pirates.