Continuity mistake: When Willow is out with Kennedy, Willow tells her that she doesn't get why she likes her. As she says "I still don't get it", she pulls her hair back over her left ear. Then when she says "Why you like me" in the following shot, her hair is hanging back down over her left ear again.
Continuity mistake: When Buffy falls down after the Master bites her, you can see her fall, then hear her hit the dry ground. But then a few shots later she falls again and this time into water.
Continuity mistake: When the detective is interviewing the woman in the alley, he mentions that the murder took place "last night". In "Bad Girls", we see Buffy visiting Faith the day after the murder, and that night is presumably when she has the dream about drowning, so by the time the detective is asking this question it is actually two nights after the murder, not one.
School Hard - S2-E3
Continuity mistake: When Buffy and Willow are studying at the Bronze, the position of Buffy's pencil changes between shots after they leave their table to go dance. Nobody else goes to their table between these shots.
Continuity mistake: At the beginning of the episode Buffy is thrown against a 'No Trespassing' sign and the sign is all crinkled, the vampire also punches it but later in the episode we see the same sign except that it looks brand new.
After Life - S6-E3
Continuity mistake: When Dawn and Buffy were talking in Willow and Tara's room, Dawn's necklace went from being above her top, to underneath her top.
Continuity mistake: When Wesley and Cordelia kiss, after a few seconds they freeze in place. Cordelia has her left arm around his waist, we see a shot of her face for about a second with her arm definitely angled downwards, then we cut to Wes' face and her hand's now on his neck. (00:25:20)
Continuity mistake: As the Trio are discussing their plans near the end of the episode, Jonathan's arms are crossed in closeups and in other positions in wide shots. (00:36:35)
After Life - S6-E3
Continuity mistake: Watch Spike's hand when he punches the wall. The punch lands with his middle knuckle in the wall, but when he looks at his hand it is mostly the largest knuckle that is bleeding. (00:24:55)
The Dark Age - S2-E8
Continuity mistake: At the end of the episode, Buffy complains to Willow and Xander that she will have to blow her allowance on getting the tattoo removed before her Mom sees it. Moments later when Buffy is talking to Giles, the tattoo is gone. (00:40:45 - 00:42:30)
Dead Things - S6-E13
Continuity mistake: As Warren is prowling the bar, the tie camera shows a redhead walking past and then a man in a white shirt sitting at the end of the bar in the background. A moment later Warren sees Katrina sitting there. (00:08:20)
Continuity mistake: When the Judge is blown up, Drusilla and Angel leap from the balcony. In mid-air, they somersault and their backs are facing the ground as they fall, but a second later they land on their stomachs.
Once More, With Feeling - S6-E7
Continuity mistake: In the episode 'Once More, With Feeling', when Tara checks out Lethe's Bramble in the book at the Magic Box, she holds the sprig facing to the left in the close-ups, and facing to the right in the long shots. (00:32:30)
Lover's Walk - S3-E8
Continuity mistake: In the scene where Xander and Willow are stuck in the factory Xander wakes up you'll notice that the blood on his side burn closest to his ear constantly changes lengths from shot to shot. It goes from under the chin to slightly below where the blood on the other side of his side burn is. (00:30:30)
Continuity mistake: In the scene where Anya is undressing a sick Xander in his basement, she lifts up his shirt and says 'Help me get your trousers off.' During the following conversation, in the close-up shots his shirt is lifted far up on his chest, but in the wider shots it's covering his whole stomach.
Continuity mistake: When Anya is confronting Dawn about Xander's disappearance and the demon boy leaves, he walks past Dawn and her attention is on Anya but in the next shot you see him walking away from behind and his sleeve is still in the shot as Dawn turns back to Anya.
The Harsh Light Of Day - S4-E3
Continuity mistake: When Spike is in the area where the gem is located, he walks to the right of entry hole, where he finds the gem. Then Harmony appears from the right side of the screen, where there's obviously no entrance.
Chosen answer: From what we see in the series, certain girls are identifiable as potential Slayers - Kendra clearly fell into this category. The identification method is presumably mystical in nature, but the Watchers' Council are pretty effective at that sort of thing, so they're quite good at tracking down the potentials ahead of time. Not perfect, though - it does appear that Buffy herself may have slipped through the net - certainly she had no inkling of what she was until she'd already taken on the role of Slayer. It is possible, however, that this was actually cultural - an American family would hardly be likely to turn over their daughter to some strange man for 'training', so the Watchers might have chosen to keep an eye on her covertly, whereas some other cultures (like Kendra's Jamaican parents) might be more willing to believe.
Tailkinker ★