Revealing mistake: When all the vampires are saying "for the dark", and one gets staked, there's a mark on his shirt where the stake's about to come through before it actually happens. Plus Buffy's hands are in the wrong place for her to have pushed that stake through, as well as there being no stake in her hand when the vampire gets dusted. Not only that, but the mark isn't even close to the vampire's heart to begin with. (00:34:50)
Continuity mistake: There are four other nuts lying on the ground around the hole at the feet of the 790 Robot where Stanley had been trying to throw them into the hole. When talking with the prisoner transporter woman, he throws another nut at the hole and makes it in, and in the close up of the hole the nut that was the furthest to the right vanishes while the other three remain in the same spot. (00:11:40 - 00:13:00)