It took three months to build all eight elephants. Two were animatronic and can make life like movements operated from a control system, while the other six are static and were made out of fiberglass.
While filming the parachute scene, the parachute failed to open for three of the six fiberglass elephant replicas during the first three takes of the scene. This resulted in having three out of the six replicas getting damaged when they didn't land on the ground safely.
During the negotiations to buy Bo-Tat the insignia on Doyle's beret is reversed. The insignia is of the 5th Special Forces Group and is a diagonal yellow stripe with three scarlet stripes in it going from the top left (as seen by the observer) to the lower right.) Doyle's is going top right to lower left. (NOTE: It happens that the Vietnamese flag is yellow with three horizontal red stripes.)
Any time they are carrying their rifles, Danny Glover and the others carry properly with their finger extended off the trigger. Ray Liotta constantly has his finger on the trigger. Against all rules of gun safety.