Actor Wayne Hapi who played "Ariki" had no previous acting experience before his debut in 'The Dark Horse', however as an ex gang-member he did have direct experience with the film's content. Wayne applied for an audition via email after Casting Director Yvette Reid placed a job listing at WINZ "seeking Maori Men aged 50-65yrs, tattoos and criminal records welcome!". Wayne was honoured with a nomination for Best Supporting Actor at the 2014 New Zealand Film awards.
At the request of writer/director James Napier Robertson, actor Cliff Curtis gained almost 60 pounds and stayed in character for the entirety of the shoot to portray Genesis.
Cliff Curtis played Uncle Bully in 'Once Were Warriors', a movie which also included the art department/ set hound used in Dark Horse. That dog's name is Rudi.