Continuity mistake: Towards the end of the episode when Buffy is running along the rooftops trying to catch up to the school bus, we see an overhead shot of one of the buildings collapsing just before she jumps off it. In this shot, Buffy is not holding the scythe that she used to kill Caleb. Once she jumps the rooftop however, she is holding it in her right hand.
Continuity mistake: During Anya's pep talk to the Potentials, Andrew draws crude illustrations to visualize what she is saying. One the second page that uses to draw a picture of the sun, the top of the previous page that's folded over the back of the board changes from being folded straight to folded at an angle between shots.
Continuity mistake: When Buffy is discussing the Turok-Han with the potential Slayers in her dining room, one of them says that it almost killed Buffy. Rona then spreads both her arms out and says, "What chance do we have?" In the following shot, her left arm is down by her side and her right arm is resting on the dining room table.
Continuity mistake: In the scene where Willow and Tara are at the old High School looking for Riley, Willow uses magic to light up the hallway. Tara then asks Willow how she did it. As Willow tells her that she taught her, she tucks her hair behind her right ear. Then after Tara says, "I taught you teeny Tinker Bell light", Willow's hair is hanging back down over her right ear.
School Hard - S2-E3
Continuity mistake: When Spike appears at the Bronze and lures Buffy outside, she runs past her table which has her jacket on it. But once she is outside she suddenly has her jacket on.
Continuity mistake: In episode 'Same Place, Same Time', Gnarl cuts Dawn across the stomach paralysing her and ripping her shirt, but when Buffy and Xander are carying her home there is no tear in her shirt or any blood. Also when Buffy goes back to kill Gnarl he tears her shirt but seconds later the rip has gone.
Continuity mistake: In the last episode of Season 5 we see Spike thrown off the tower by Doc. Spike somehow manages to change from black trousers and boots into blue jeans and white shoes mid-air. He's back in black by the time he hits the ground. (00:35:45)
Continuity mistake: In the season five episode Triangle, Anya says she has never driven before, but in Graduation Day part one she tells Xander she has her car right outside. (00:22:50)
Continuity mistake: In the episode Prophecy Girl, during Buffy's rooftop fight with the Master, her shoes change in between shots from white heels, to black boots when she's kicking him, back to white heels. (00:41:35)
Never Kill A Boy On The First Date - S1-E5
Continuity mistake: When Buffy is talking to Owen at the end, there is a woman wearing a red/black checkered jacket, sometimes carrying a red bag, walking up the stairs behind Owen several times. You can also see her behind Buffy in shots facing her. (00:40:25)
Continuity mistake: When Willow hides under the table in the classroom after fleeing The Pack, we see that it is on legs and doesn't touch the floor. Yet when Xander comes in and scans the room, he sees the table but Willow's feet aren't visible, even though they should be judging by the height of the table from the floor.
Once More, With Feeling - S6-E7
Continuity mistake: From the start of the second scene in the Magic Box, the doughnut and cruller on Xander's plate constantly switch places. (00:03:35 - 00:05:50)
Continuity mistake: When Dawn is in Principal Woods' office to talk about the accident, she gets up and leaves. Her bag is still hanging from the chair, but she has it in the next scene.
Continuity mistake: At home Buffy helps her mother open a crate. She tears off the cover and leaves it hanging by the side. Next shot the lid is back on. Not nailed anymore of course, but there was no time to put it back on.
Continuity mistake: In episode 'Anne', when fighting the hell dimension demons Buffy's shoes change from trainers to plain pumps in different shots.
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 ★