Corrected entry: At the start of the scene where Ned is fighting the German, Ned is given a gun to fight with and his own gun is put in the front of his pants. Later in the scene after he loses the gun given to him, he draws his own gun out of its holster on his side, not from the front of his pants.
Corrected entry: When the bad guys are beginning their celebration just before the Three Amigos take them on, there is a scene where people are holding a series of ropes attached to a tall pole. About a minute or so later, when the Amigos are climbing onto the wall around the bad guys' compound, you can see all these ropes are suddenly hanging between the pole and the roofs of the surrounding buildings. How did the people get the ropes up there so quickly?
Corrected entry: When the Three Amigo's swing on the ropes in the fort at the end of the movie, Dusty swings into a room, but his rope goes right through the roof. Then, when Ned goes, his feet get stuck. This should make him facing the sky, but he is facing down.
Corrected entry: In the scene where the three amigos are all in the bed talking about what each one is going to do with their share of the money, Lucky says he is going to "buy a big, shiney silver car." However, the movie is set in the twenties and cars were brand new. You would be hard pressed to find a big car, let alone a silver one.