The film is based on the book "Goon: The True Story of an Unlikely Journey into Minor League Hockey" by Adam Frattasio and Doug Smith. Footage from Smith's career as a hockey enforcer is shown during the films credits.
In an interview with hockey blog Puck Daddy, Liev Schreiber notes that he was inspired by former hockey enforcer Bob Probert. As an homage to the player, he taped his wrists for the film, just as Probert had done when he played.
The "polite" offer to fight Glatt received from Albany Patriots' Huntington (Georges Laraque) is actually based on a real fight in the NHL when Georges was playing for the Phoenix Coyotes and was mic'd for the game. He "politely" asked Raitis Ivanans from the Los Angeles Kings if he wanted to "go" then wished him "good luck" on Nov 30, 2006.
A great majority of the cast is comprised by Canadian actors, including the well-established actors in Hollywood like Jay Baruchel, Kim Coates, Alison Pill and Eugene Levy. The only non-Canadians in major roles are Minnesota-native Seann William Scott and New Yorker Liev Schreiber. Ironically, Baruchel plays an American character (a thickly-accented Massachusetts native) in the film, while Schreiber plays a Canadian character.
The scene where Rhea sheds crocodile tears during a press conference was a reference to NHL player Todd Bertuzzi. Bertuzzi, playing for the Vancouver Canucks at the time, punched Colorado Avalanche's Steve Moore in the back of the head during a game causing an injury that would end Moore's career. In a press conference afterwards, an emotional Bertuzzi tearfully apologized for the incident, which cost him a $500,000 salary deduction and a 17 month suspension.
The character of Doug Glatt plays for two teams in the movie: The Orangetown Assassins, who wear orange and black uniforms; and the Halifax Highlanders, whose logo is the letter H with a dot on the right side and wings on the left. Both are allusions to the NHL team Philadelphia Flyers, who have a similar logo and wore a similar style of uniforms in the past.
The trivia item below may give away important plot points.
One of the plot points is Liev Schreiber's character being suspended for 20 games for slashing an opponent in the head from behind. NHL enforcer Marty McSorley was suspended for 23 games in 2000 after doing the same thing. The victim of the incident, Donald Brashear, suffered a grade three concussion from the slash and falling and hitting his head on the ice. Marc-André Grondin's character suffers the same injury at the hands of Schreiber's character, but in a different incident.