Nightmares - S1-E10
Continuity mistake: In the beginning dream sequence, when Buffy is surprised by the Master and backs up into the wall, watch her two pigtails. As the scene cuts back and forth between Buffy and the Master, her pigtails move from behind her shoulders to in front of her shoulders and back several times. First they're both behind her shoulders, then only one is behind, then both are in front, then one moves back behind again, etc. Obviously multiple different takes were cut together in editing.
Nightmares - S1-E10
Continuity mistake: Buffy's history teacher is not the same person from episode 1 or 9, originally a woman, the teacher is now a man. Cordelia also notes Buffy doesn't know where the class is due to ditching, but we saw Buffy in her history class with Cordelia in The Puppet Show. How could Buffy not know where her class is only 1-2 weeks later?
Out Of Mind, Out Of Sight - S1-E11
Visible crew/equipment: When Buffy and Cordelia enter the mop closet you can see the shadow of the boom microphone on the wall near Buffy's head (left side of screen). (00:31:44)
Out Of Mind, Out Of Sight - S1-E11
Visible crew/equipment: At the very end, as the invisible girl gets taken along a corridor by the FBI agents, check the top of the screen - a boom mike creeps in as the agent says his line, then is withdrawn.
Out Of Mind, Out Of Sight - S1-E11
Continuity mistake: When the gang are in the cafeteria and Giles comes along, Buffy's hands instantly change positions as she says "I love it when he says that!" Then, in the very next shot, a drink suddenly appears in her hand that wasn't there before.
Out Of Mind, Out Of Sight - S1-E11
Audio problem: When Cordelia is tied to the chair at the end of the episode from a side view you can see her mouth 'Marcie' but can't hear it and in the front shot she says 'Marcie' again.
Out Of Mind, Out Of Sight - S1-E11
Continuity mistake: When Cordy notices the word "Learn" in The Bronze and asks "What does that mean?" the positions of the ropes around her arms changes instantly between cuts.
Out Of Mind, Out Of Sight - S1-E11
Audio problem: When the invisible girl writes "Listen" on the chalkboard, the chalk sound effects don't match the writing for the last few strokes. (They're about a half-second too "early.").
Out Of Mind, Out Of Sight - S1-E11
Continuity mistake: When Buffy finds the invisible girl's "home" in the ceiling and picks up her flute, the position of everything on her bed changes between the initial closeup we saw and the shot of Buffy picking up the flute. Ex. In the initial closeup, the flute is on an open case, while in the shot where Buffy picks it up the case is closed. All the sheet music is in a slightly different position. A cylindrical object appears next to the flute that wasn't there in the initial closeup, etc.
Out Of Mind, Out Of Sight - S1-E11
Continuity mistake: When Xander makes the joke "Maybe it was a vampire bat!" in the cafeteria near the beginning of the episode, a sandwich suddenly appears in his previously-empty hand between edits.
Out Of Mind, Out Of Sight - S1-E11
Visible crew/equipment: After Cordelia wins May Queen, Buffy, Xander and Willow are talking, and right before she walks away, you can blatantly see an on-set light reflector being reflected in Buffy's sunglasses.
Out Of Mind, Out Of Sight - S1-E11
Continuity mistake: After Buffy cuts herself out of her chair, she unties Cordy's left wrist. The scene cuts away to Giles, Xander, Willow and Angel. When the scene cuts back to Buffy and Cordy, suddenly Cordy's wrist is tied again. There's no indication that it was retied in the meantime.
Out Of Mind, Out Of Sight - S1-E11
Continuity mistake: When Cordy and Buffy are tied up, at one point Marcie the invisible girl punches Buffy. As it cuts from a closeup of Buffy back to a wideshot, the position of Buffy's head and the expression of her face instantly changes between cuts. She goes from having her head crooked with a pained expression and her eyes half-shut to having her head straight with a shocked expression and her eyes wide open.
Out Of Mind, Out Of Sight - S1-E11
Visible crew/equipment: When Giles, Willow and Xander are trapped in the storage room with the leaking gas, at one point you can blatantly see a massive set-light reflected in Giles glasses. (This is fairly common, as often lights are reflected in his glasses, but it's particularly noticeable here).
Out Of Mind, Out Of Sight - S1-E11
Continuity mistake: When the invisible girl pushes Buffy, and she falls through the ceiling and onto a table, the position of Buffy's arms changes slightly between edits when it cuts to a high-angle shot of her knocked out. Some of the debris around her also changes position.
Out Of Mind, Out Of Sight - S1-E11
Audio problem: When Cordy and Buffy are talking and Cordy says "Well it beats being alone all by yourself, " pay attention. It's clear that part of the line was dubbed in, as there is a very hard cut between the words "Well" and "It."
Out Of Mind, Out Of Sight - S1-E11
Audio problem: When Cordelia wins May Queen, the clapping sound effect doesn't match the students clapping in the slightest. It's far too loud considering it's a small group outside, and continues on for about two seconds after the students clapping.
Out Of Mind, Out Of Sight - S1-E11
Visible crew/equipment: When Angel and Giles talk in the library, in multiple shots you can see stage lights and light reflectors being reflected in Giles' glasses. (This is actually fairly common in many of his scenes, but it's particularly noticeable here).
Out Of Mind, Out Of Sight - S1-E11
Continuity mistake: This is subtle and hard to notice. When Buffy is explaining that something bumped into her in front of the school after Giles explains what it's like to be touched by a ghosts, pay attention to Xander. In the first shot, he's standing about two feet back from Buffy and his left shoulder is behind Willow. In the next shot he's suddenly much closer to Buffy and Willow is no longer in front of his left shoulder.
Out Of Mind, Out Of Sight - S1-E11
Continuity mistake: When Harmony is pushed down the stairs, she suddenly goes from in front of to behind the garbage can at the bottom instantly between cuts.
Chosen answer: He had larangitis and because of the shooting specifications they had to have him shoot the scene with a bad throat, they then re-recorded his lines and dubbed them. At various points during the scene and indeed the episode you can see him touch his throat or rub it.