Many of the players in the game scenes (as well as the Hanson brothers) played for the Johnstown Jets, a team in the now-defunct minor-pro North American Hockey League. The Charlestown Chiefs were based on the Jets.
Though decried by much of the NHL upon release - many league higher ups felt fans would lump the brawl-filled 1970s NHL with the brawl-filled minor league featured in the film - the movie is still a staple on NHL buses and team charters. It's not uncommon for NHL players born years after the movie's release to name it as their favorite movie. In locker rooms, players refer to reporters who write an untrue rumor with conviction as "Dickie Dunn."
Bruce Boudreau, head coach of the NHL's Anaheim Ducks, appears in the film wearing #7 for the Hyannisport Presidents. Boudreau was one of several players for the Johnstown Jets minor league hockey team that were used as extras.
According to David Hanson (during a Q&A on his 2008 book tour) much of the Hanson brothers' on screen antics were unscripted and improvised on the set. For example the toys in the hotel room were the Carlson brothers' own.
Near the end of the film, the radio broadcaster is interviewing one of the Hansen brothers in the locker room, and he refers to Charlestown as "the flood city". Slap Shot was filmed in Johnstown, PA (of 1889 Johnstown Flood fame), and the year that Slap Shot opened (1977), Johnstown was flooded for the third time in its history (the other two being 1889 and 1936). Johnstown's unofficial nickname (even prior to Slap Shot's release) is "the flood city."
Brothers Jack, Jeff Carlson and Steve Carlson were originally slated to play the Hanson brothers. However, Jack was called up by the Edmonton Oilers shortly before filming began. His part went to another member of the Johnstown Jets, David Hanson, who was supposed to play Dave "Killer" Carlson. Actor Jerry Houser was hired for that part.
Universal Pictures offered Steve Carlson, Jeff Carlson and David Hanson the chance to star in their own spin-off film. But all three turned it down to return to their professional hockey playing careers.
During rehearsals, Yvon Barrette was seriously injured when a puck hit him in the knee. Barrette was worried that he would be replaced with another actor. But George Roy Hill postponed shooting scenes featuring Barrette so that he could return to the film when he recovered. Barrette returned to filming 10 days later. But to prevent any further injury, Barrette was doubled by Ronald L. Docken during the hocking playing scenes.
Peter Strauss auditioned to play a role in Slap Shot (1977) but broke his leg whilst skating in the audition. He later appeared on The Tonight Show (1962) with his leg in a cast to lament his plight, and marvelled that the much older Paul Newman skated rings around him without so much as a scratch.
The character of "#7 Clarence 'Screaming Buffalo' Swamptown" was played by Joe Nolan who, during a brief minor league career in the 1950's, accumulated almost one thousand penalty minutes in 6 seasons, including one with the Johnstown Jets.
Allan F. Nicholls wore a helmet so he would not be mistaken for Jerry Houser, since they both had curly brown hair. In addition, Nicholls decided to grow a Fu Man Chu Mustache in honor of his idol, then Montreal Canadiens' defenseman Larry Robinson (Robinson wore that style mustache at that time).
Al Pacino showed interest in the lead role but fell out with director George Roy Hill after he was asked if he could ice skate (Pacino considered the question "facetious"). Pacino later expressed regret that he had missed out on the film.
A significant portion of songs in the theatrical release, as well as versions shown on T.V., were replaced by other songs on the VHS and DVD release. They were finally restored for the 25th Anniversary editions.
Shortly after the film opened, the Jets had to suspend operations for one season because a flood damaged their ice-making equipment. After a final year as the Johnstown Red Wings, the franchise was idled in 1980. It was eventually revived in 1987 as the Johnstown Chiefs.
The character Ned Braden is named for Ned Dowd, the brother of the film's writer, Nancy Dowd. Ned Dowd was a player for the minor league team the Johnstown Jets whom the Charlestown Chiefs are based on.
Paul Newman's player-coach character Reggie Dunlop was based on John Brophy, a long-time minor-league player and coach. Brophy later coached the NHL's Toronto Maple Leafs for 2 1/2 seasons. Michael Ontkean played college hockey at the University of New Hampshire.
The Championship Trophy presented at the end of the movie was, in reality, the Lockhart Cup, which was representative of the North American Hockey League championship. To this day, it sits in the basement recreation room of Danny Belisle, where it has become a flower pot.
In the scene where the referee was told to listen to the song, the red white & blue jersey belongs to Former WHA referee Ron Fournier. The production company personally called him to get the jersey but it was after a phone call to the league's front office that he accepted. He removed his name on the back but kept his number on it.
Steve Carlson became the Head Coach of the Johnstown Chiefs East Coast Hockey League Team in 1988 until 1992. The Chiefs played their home games in the Johnstown War Memorial arena where the movie was filmed. The Chiefs franchise played their home games in the same arena from their founding in 1988 until 2010, having since moved to Greenville, South Carolina. Beginning with the 2010-2011 season, the ECHL's Wheeling (West Virginia) Nailers, a former Chiefs' rival, will play 10 of their 36 home games at the War Memorial arena.