Encontrado no trivia do IMDB:
Zack Snyder wanted to cast his 300 (2006) star Gerard Butler in this film and even promised him a role. When all the roles were cast and Butler didn't have one, Snyder cast him in Tales of the Black Freighter (2009), which is based on the comic-within-a-comic from the Watchmen graphic novel and was released on DVD around the time Watchmen was released in theaters.
Então Gerard apareceu em TotBF , que é mostrado em todo o filme. Mais informações aqui .