Seen it before? No.
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Some have called it the "Mexican Pulp Fiction". It's really three intersecting movies - well, in theory. The three plot lines come together in a violent car crash that is the climax of one plot, the start of another, and is witnessed in passing by the third. All three plots involve dogs in some way.
#1: Octavio y Susana. Octavio (Gael García Bernal) gets involved in the underground dogfighting circuit; makes a lot of money but then gets into trouble. Also he tries to steal his brother's woman Susana (Vanessa Bauche). His brother is a creepy asshole, and a criminal, but so is Octavio, so why should I sympathize with him? Oh, I guess the brother hits her and cheats on her, just as sort of a "kick the dog".
#2: Daniel y Valeria. While escaping from the gang, Octavio smashes into Valeria's (Goya Toledo) car, messing up her leg. Valeria is a model of some sort, having been introduced in an Unmotivated Close-Up on a talk show. Her dog gets stuck under the floorboards of her condo. Her boyfriend (Álvaro Guerrero) seems to take a very laid-back approach to getting it out.
#3: El Chivo y Maru. A craggy hitman known as "El Chivo" (Saddam Hussein) has to carry out a job, but he gets interrupted by the car crash. He steals Octavio's dog, and he has a daughter, and... eh, whatever, I didn't care by this point.
Don't see this movie if you're averse to animal cruelty; dogs suffer in this movie. (it says "no animals harmed", but I don't think I believe them.)
Position on the list: 163
While we're on the subject of Alejandro González Iñárritu: Babel. Saw it 2 years ago and I'm still mad. What did that stupid Japan plot have to do with anything? dammit.