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Arnold Schwarzenegger worked a little more than a week on the movie. On the first film, Schwarzenegger worked half a day (as he was still Governor of California at the time), and on the second film, he was on-set for four days. He cited his dissatisfaction with the third movie and the poorly written role for his character in it as reasons not to return for the fourth, The Expendables 4 (2023), although he maintained that he still loves the franchise.
Bruce Willis was set to reprise his role of Mr. Church, at a salary of $3 million ($750,000 per day for four consecutive days). When he demanded $1 million per day instead, Sylvester Stallone and the producers refused, and he left the film. Within three days, Stallone was able to get Harrison Ford to replace the Church role as a new character. Ford's "short notice" quip, as used in the trailer, alludes to these events (which were well publicized long before the film premiered).
While shooting an action scene in a truck, Jason Statham almost drowned when the truck fell into the sea after brakes failed.
As his character in the film, Harrison Ford is a skilled pilot in real life. In fact, Ford has conducted some search-and-rescue missions, just like his character does in the film.
Sylvester Stallone tried to get Wesley Snipes to play the role taken by Terry Crews in The Expendables (2010). Crews went on to play Hale Caesar after Snipes declined due to legal matters related to his tax-evasion charges that prevented him from leaving the United States without the court's permission. Wesley Snipes got the role as "Doc" shortly after his release from prison. In a scene, Dolph Lundgren's character asks Snipes' character what he was locked up for to which he replies "tax evasion".
When he is asked about the whereabouts of Church (portrayed by Bruce Willis in the two previous films), Max Drummer (Harrison Ford) answers that "He's out of the picture." This is an in-joke about the fact that Willis' character was written out of the film and replaced with Ford's character.