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Stupidity: Lyra says, "We can't call the police. We broke into our neighbour's house. There's a dead body downstairs and there's an alien running around." Given that everything can be attributed to the alien, the police do not know (or have to be told) the friends broke into the house or that they "weren't supposed to be there" - they can merely say they heard loud noises. The friends stay in the house, hiding and fleeing from the alien. (00:32:47)

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Stupidity: After Lyra and her friend escape from the alien and get into the car, they don't immediately lock the doors. A little later, one says, "He's coming. Lock the doors." They also leave the car's interior roof light on, making it easy for the alien to spot them. (01:06:55 - 01:07:32)

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