Although neither Las Vegas nor Alabama figures in the plot, these two areas did play a special role in the film. Robert Duvall (Shrike), the mercenary hired by the plumbers to guide their rescue mission, to prepare for his part in the movie, visited Las Vegas to attend a convention held by Soldier of Fortune Magazine, the Bible of mercenaries, weekend soldiers, and weapon afficionados. There, Duvall had a chance to familiarize himself with the firearms and knives used by mercenaries, meet the men who have devoted their lives to fighting counterinsurgency and guerrilla wars, and pick their brains for ideas. Duvall also made a special trip to a mercenary camp in Alabama, where he had a chance to observe these professionals in action as they trained for future combat. One of the outcomes of these trips was a new look, including a shaven head, and a new catalogue of mannerisms, which Duvall brought to the film with stunningly realistic results.

Thomas F. Wilson appeared in this film and Psych (2006) season four, episode eight, "Let's Get Hairy", which is a reference to this movie's title.

Director Stuart Rosenberg didn't have his name on the movie, and was billed as "Alan Smithee", which is a pretend film industry name used by directors who don't want their names on a movie. "Variety" reported "Stuart Rosenberg took his name off the credits, reportedly due to a contretemps during post-production."

For added authenticity, the producers hired a paramilitary expert, David Webster, as the movie's unofficial advisor in jungle warfare.

The man who piloted the plane used to transport the group into the jungle for the movie was an ex-mercenary.

Although the setting of the story is unidentified, Screenwriter Charles Robert Carner spent considerable time in Colombia researching the yarn, which had its origins in a concept suggested by Blatt and Singer during the early 1980s in the pre-Rambo era. In Colombia, Carner was introduced to people who worked both sides of the law in fighting and carrying out the lucrative contraband trade that has spread from Latin America to the streets and suburbs of the United States.

Thanks to his membership in the Cousteau Society, Charles Robert Carner was able to contact American and local newspaper reporters, who were able to provide him with valuable leads and contacts. In this way, Carner was able to familiarize himself with methods of operation and politics, which frequently resulted in sinister and dangerous consequences.

The movie's production "project was (originally) planned as a film by Samuel Fuller, writing and directing, in 1981. He is credited with co-writing the story (with Mark Feldberg)" according to "Variety".

When the film was in pre-production, the producers decided to use the area of Veracruz, Mexico as the principal setting. For one thing, they were familiar with the area, having shot the acclaimed miniseries Sadat (1983) there. They had discovered that Veracruz, which had been built by the Spaniards in 1599, and was located near the site of Cortes' original landing on the Mexican mainland back in 1519, still had its colonial ambience. Its public buildings, churches, and plazas could be traced back to the seventeenth and eighteenth centuries, when Spain was the ruling colonial power.

The surrounding area of Veracruz, Mexico included rivers and jungle which figured prominently in the story. The filmmakers added several features to the landscape. They built two jungle airstrips for the small planes used to transport the American would-be rescuers. The fields were constructed to appear as if they had been around for a long time. The company also constructed an elaborate jungle compound, headquarters for Carlos Ochobar (Guillermo Ríos), the renegade revolutionary who kidnapped Harry and the American ambassador to protect his lucrative contraband trade, and is willing to kill if necessary.

The friendly invasion by an American movie company for the shooting of this picture, was only the latest of many less welcome "visits" by foreigners experienced by Veracruz, Mexico throughout the centuries. During the seventeenth and eighteenth centuries, it was a popular target of pirates seeking treasure and women. During the nineteenth and twentieth centuries, the French, British, and Americans landed there. In 1847, American General Winfield Scott launched his campaign of conquest at the start of the Mexican War, fanning out from the streets of Veracruz. In 1861, Austrian Archduke Maximilian used Veracruz as a jumping off place in his plan to become Emperor of Mexico. In 1914, American troops landed there again, sent by President Woodrow Wilson after American sailors had been arrested in Tampico. But for the film company, the welcome mat was spread out as heavy equipment was trucked in via El Paso, Texas, and over the twisting mountain roads, down to Veracruz.

Washington, D.C., with its miles of gleaming government buildings, served as a backdrop for the group's frustrating visit to the nation's capital when they seek help for Harry's rescue. Because cameras were not allowed inside the buildings, the offices of congressmen and state department officials were studio reconstructions.

The "pic was lensed in Mexico and Illinois in 1985" according to "Variety".

Locations in the movie included Aurora, Illinois, which represented the characters' hometown of Argus. Here, Blatt and Singer rented an entire factory to stand in for the pipe and valve factory, where the plumbers were employed before they leave for South America.

Accordin to Wikipedia, the movie was one of several 1980s films that centered on civilians partaking in hostage rescues, without the help of the U.S. Government. Other similar films that were released around the same time were Uncommon Valor (1983), Rambo: First Blood Part II (1985), Iron Eagle (1986), The Rescue (1988), and Missing in Action (1984).

Thomas F. Wilson and Gary Busey did not get along during the making of the film. Wilson references this in his Question Song by saying "Who is the nicest famous guy you know? Adam Sandler. Who is the biggest jerk? Gary Busey."

The movie's title is heard in a passage of dialogue within the film. It's said by Harry's younger brother Corey, who says: "I mean for God's sake, if I was the one being held hostage, if any of us were, Harry'd be on the first goddam plane to come and get us . . . Let's get Harry!"

A Franchi SPAS-12 shotgun is used prominently throughout the film. It was blank-adapted to fire then-Hollywood-standard 12 gauge Stembridge Blanks. However, during filming in Mexico no Stembridge Blanks were available and locally manufactured blanks had to be used. These were too powerful for the standard blank adapter in the SPAS-12's barrel muzzle. In one scene as Robert Duvall fired it, the muzzle burst open loudly and the end of the barrel split. According to the movie's weapons specialist, Terry Sepanek, Duvall said "F*** this!" and threw the shotgun down.

The football game, the guys were watching in the den, was a game between the Minnesota Vikings and the Chicago Bears in October of 1985, the Bears defeated the Vikings 27-9, and won Super Bowl XX. The Super Bowl was in January 26 of 86 and the Chicago Bears beat the New England Patriots 46 to 10.