Several scenes were filmed in the High Security Prision of Matamoros, México, with real inmates working as extras and making small parts.
One of the inmates of the Matamoros High Security Prision, known as Tun Tun, was helped by the cast and crew of the film to obtain his freedom. Tun Tun, a small man that appears in the film as one of German's bodyguards in prison, was in jail because he tried to steal a bike and was unable to pay the fee. The cast and crew created a found named "Free Tun Tun" and everyone gives 5 dollars to complete the fee. Tun Tun was released the final day of shooting in the prison. He didn't expect it.
Adal Ramones's popularity, as the leading man of the TV show Otro rollo con: Adal Ramones (1995), created such a furor in the locals of Matamoros and Brownsville, that many people that approached to the crew asked frequently if that was "la película de Adal" (Adal's movie). Hundreds of people surrounded the locations, specially the days when Adal Ramones didn't have scenes to shoot.
During one of the shooting scenes, a local of Matamoros who played a gunman was questioned by the special effects coordinator, Alejandro Vazquez, about the credibility in the way he pulls out the gun. The local replied (in Spanish), "Look, I have killed three fellas. And you?" That ended the discussion.
The second unit was known as "Micro crew". When a third unit was created, with only six people, this last unit was named "Atom crew"