Continuity mistake: When the group is debriefing about their first Dracula encounter at Giles', Anya is sitting on the sofa with her hands crossed on her lap. In the next shot she has her arms straight with the palms of her hands on the sofa cushion, fingers towards the back.
Visible crew/equipment: In the scene where Spike escapes from the initiative a black curtain can be seen to the right of the screen after the other vampire is release from his cell. The curtain serves no purpose to the set or scene and it disappears in the next shot.
Deliberate mistake: In the fighting scene, the glove of Myhnegon is used by the new watcher who directs it toward the ceiling of Angel's living quarters where there is a huge skylight. The skylight is not seen in any other episode and its presence would have burned him on other occasions.
Character mistake: Giles picks up the potential slayer Chao-Ahn from Shanghai in Episode 7.12, "Potential". However, when she arrives in Sunnydale (Episode 7.14, "First Date"), the language she speaks is neither Mandarin nor Shanghainese (the two main languages spoken in Shanghai), but Cantonese, which is not widely spoken there.
Continuity mistake: Near the end, when Spike takes the cup of blood from the fridge, we can see that it is full to within a 1/4 inch of the rim. However, when the shot changes and he drinks it, he tips the cup almost 45 degrees before putting his lips to the cup and drinking. If the cup had been as full as previously shown, the blood would have begun pouring out long before Spike ever drank form it.