Night of the Sentinels: Part 1 - S1-E1
Factual error: When the Sentinel reaches out to try to grab the dog, it smashes its hand against the grass and produces numerous cracks in the lawn with a metal clanging sound. Neither of these things would happen. The grass would have a bunch of divots in it, and the sound would be similar to something heavy falling in dirt. (00:02:09)