Due to the film's modest budget, Axl Rose donated the use of Guns N' Roses' "Sweet Child O' Mine" free of charge for the final match.
Darren Aronofsky revealed that Mickey Rourke was the first choice to play Randy "The Ram" Robinson but the studio wanted Nicolas Cage. Aronofsky fought to have Rourke as "The Ram", and ultimately won out.
Mickey Rourke actually "blades" (cuts his own forehead with a razor) in this film to add realism to the role. This is also known by the wrestling term as "gigging," "getting color," or "juicing".
Scott Siegel, the actor who portrayed a steroids dealer in the film, was arrested a few months after the film's release for steroids possession and assaulting federal officers.
Hulk Hogan claimed on The Howard Stern Show (1990) that he was offered the role of Randy "The Ram" Robinson. Hogan claims he turned down the role because he felt he wasn't the right man to portray the character. Darren Aronofsky publicly disputed this, stating that Hogan was never considered, and that Mickey Rourke was his only choice for the role.
Robert Siegel: The film's writer makes an appearance at the start of the film as a fan getting an autograph from Randy "The Ram" Robinson (Mickey Rourke).
Darren Aronofsky: [angles] This movie features familiar Aronofsky trademarks of the point of view angle and free-held camera.