Controversial because of the fact it depicts dogfights, the dogs seen fighting each other were actually just playing. Careful editing makes it look a lot more vicious. Their muzzles were also covered with very fine fishing line so they were unable to bite each other.
All the images shown on the TV sets during the picture are commercials. These commercials were also directed by Alejandro González Iñárritu. They include a TV station promotional, an ad for a bank, among others.
The first film in a loose trilogy of death, all directed by 'Alejandro Gonzalez Inarritu' and written by Guillermo Arriaga. The next two films were _21 Grams_ and Babel (2006). Between them, all three films racked up 10 Academy Award nominations.
The car crash sequence was shot with nine simultaneous cameras, including two on adjacent rooftops and one hidden in a trash barrel. A stunt driver was in the black car, while the model's car contained a remote-controlled animatronic dummy. A practice run caused the black car to accidentally tear the rear bumper off the model's car, but since it was getting late, it was stuck back on and the shot attempted in toto. This time the model's car spun around, overshot its projected target by at least 100 meters, and smashed into a taxicab parked by the side of the road. This take was used in the final print.