Director Álex de la Iglesia wanted Clint Eastwood to play himself in the film. He even offered to move to Los Angeles to shoot Eastwood's part. Eastwood, who was then working on the production of Mystic River (2003), was forced to turn down the offer.
De la Iglesia thought this was going to be a cheap movie, but in the end it cost a little more than he thought. According to Sancho Gracia, the main character of the film: "I used to say to him 'Álex you're going to ruin' and he said yes, he was going to ruin, but he was going to make the movie that he wanted".
It is based on an idea of the director himself and his usual scriptwriter, Jorge Guerricaechevarría, that came up after seeing a show for tourists in Almería, where they were looking for exteriors for the unproduced "Fu Manchú" reboot.
The character of "Julián" (Sancho Gracia) is clearly inspired by a series of real anecdotes from the biography of the actor Aldo Sanbrell, a regular at Spaghetti Western Almería.
The young man with beard, curly hair and glasses behind Laura when she talks to the camera is not Álex de la Iglesia but 'Francis Aguilar'. An Almeria-born director of short movies ("Zombeach"), he joined the crew of 800 balas and became a friend of de la Iglesia. They look so much alike that they decided to give him a cameo role to fool the audience.