Audio problem: When Joyce is about to leave for the pre-show, we hear Xander say "Have fun, but not too much fun", but his lips never move.
Audio problem: When Joyce comes downstairs and comments on the breakfast Buffy made, Dawn says 'Oh, Buffy helped,' but her mouth doesn't match what she's saying.
Audio problem: At the start of the episode when Buffy and Dawn are with Joyce in the hospital room, Dawn starts eating jelly, and when Joyce starts speaking you can see in the left hand corner of the screen Dawn talking, but no words are coming out.
I Was Made To Love You - S5-E15
Audio problem: When Spike arrives at the magic shop with a burning blanket over his head, he throws it to the ground and stomps on it, yelling, "Fire! Fire!" As he yells "Fire! Fire!" however, his lips aren't moving.
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 ★