Konlabos, the fruit used to paralyze Dwayne Johnson and Seann William Scott's characters, is actually a fruit called chirimoya or custard apple, depending on where you buy it. This fruit does not cause paralysis and is actually eaten all over the world for its delicate flavor.
According to director commentary on the DVD, Christopher Walken had never seen Willy Wonka & the Chocolate Factory (1971) and was therefore reluctant to use the phrase, "Oompah-loompahs" in his final scene. The director provided Walken with a copy of the movie, and after watching it, Walken decided to use the phrase.
Hatcher's tooth-fairy speech was a substitution for him comparing the situation to Pooh stuck in the door to Rabbit's house from The Many Adventures of Winnie the Pooh (1977) after Disney threatened to sue over it.
The film's original title was "Helldorado". It was then changed to "Welcome to the Jungle" before being changed again to "The Rundown", although it was released in several countries as "Welcome to the Jungle".
According to director Peter Berg, they were scouting a location in the Amazon forest of Brazil when they were held up at gunpoint by three locals and robbed of all cash, computers, and other valuables. After that (probably a joke) the shoot location was changed to Hawaii.
When Christopher Walken is delivering his speech about keeping his eye on the ball, the images that are shown of the gold mine workers are a reference to a series of photos from the 1980s by Sebastião Salgado that were taken at a famous Brazilian gold mine, called "Serra Pelada".
For its international release, Sony had the opening ten minutes of reel 1 reprinted so the Columbia logo would be first, and then followed by the Universal logo (it is reversed in the US prints). This was also done to accommodate the title change for international markets ("Welcome to the Jungle") which appeared directly after Beck fights the football team in the nightclub. After the title came on, the new film that was stitched to reel 1 finished and the remains of the old reel 1 continued.
Despite being a Scot in real life, and sporting a kilt and playing the bagpipes (traditionally and stereotypically Scottish activities) in one scene, Ewen Bremner speaks with a Northern Irish accent throughout this movie.
Both of the film's previous working titles are referenced in the film. After arriving in Brazil, Beck passes a sign that reads "Helldorado", and in the jungle, Travis tells Beck, "Welcome to the jungle..."
The rifle that Mariana uses to nearly shoot Travis is a 7.62x39 SKS Sporter edition. The standard SKS had a built in, non-removable 10 round magazine, while the sporter edition took the AK-47 magazines (which replaced the SKS).
When he first appears, bagpipes in hand, near the end of the movie, Declan (Bremner) paraphrases the first part of Ezekiel 33:5 - "Since they heard the sound of the trumpet but did not heed the warning".
Once seated, Declan (Bremner) then quotes part of Dylan Thomas' poem, "Do Not Go Gentle Into That Good Night" - "rage, rage against the dying of the light". Beck (Johnson) also has "Do not go gentle" tattooed on his inner forearm, which is seen in the next shot.
The director of the movie Peter Berg also directed Dwayne Johnson in an episode of the latter's HBO series "Ballers". Peter also plays a football coach in the series and Dwayne got his start as a college football player at the University of Miami.
Arnold Schwarzenegger: as a man in the club. This cameo was filmed the same day he filmed his appearance as the Terminator for the Super Bowl. It was completely unprepared. He happened onto the set that day and was asked to make a quick appearance in the film. Fans and movie enthusiasts often cite his saying "Have fun" to Dwayne Johnson as a passing of the torch to an action hero of the next generation.