Other mistake: When we first see one of the Hellhounds at the clothes store that Cordelia works at, it jumps through the window, smashing the glass, and then attacks a customer who's wearing a tuxedo. But the Hellhound attacks the customer several seconds after it smashes through the window, giving the customer a chance to escape. But the customer just stands there unaware of the Hellhound, having not heard the window being smashed.
Plot hole: After losing his soul, Angelus kills Jenny Calender's uncle, who is a descendant of the gypsy clan who cursed him. But, since there is nothing to suggest the uncle's room is in a public location, Angelus couldn't have gotten in the room without an invitation.
Life Serial - S6-E5
Plot hole: In the 3rd time loop at the magic shop, the woman looking for the mummy hand looks surprised when Buffy knows what she wants. In the 2nd time loop, the woman tells Buffy that she called the shop 20 minutes earlier and was told that they had one. Therefore at least one of the shop's staff would be aware that a woman would be arriving looking for a mummy hand.
Welcome To The Hellmouth (1) - S1-E1
Continuity mistake: When Xander is talking to the girl at the Bronze his hand is on the pole and off the pole throughout.
Revealing mistake: When Buffy and Angel are sword-fighting, the camera pans up and to the side, you can see David Boreanaz's stunt double. His hair line is farther back then David Boreanaz's.
Visible crew/equipment: After Anya teleports to the jail leaving Buffy and Xander in the forest, the shadow of cameraman walking backwards can be seen as Buffy and Xander make their way to Xander's car. Look closely, the shadow is visible and Buffy tells Xander not to be too sure about Anya being able to handle Willow tonight.
The Harsh Light Of Day - S4-E3
Continuity mistake: Right before Spike jabs Buffy in the face on the college's campus, there are a ton of people around. But after he jabs her in the face and they start fighting, all of the people are gone.
Visible crew/equipment: When Ampata agrees to go to the dance with Xander and they walk off down the hall, a shoe can be seen in the bottom right of the screen within the last few frames stepping into shot.
Character mistake: At Riley's party, Willow tells him that Buffy is wearing a halter top when she is in fact wearing a strappy top. Being a girl, and extremely into fashion at this stage in her life after her high school years, she should have known better.
Revealing mistake: Near the end of the episode when the Mayor releases the vampire from his cage and lets him cut his head in half, you can tell that the Mayor's head is a still image when it fixes itself. The expression on his face doesn't change at all and looks completely unrealistic.
Revelations - S3-E7
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. (00:38:10)
Other mistake: The Master's skeleton, before it is destroyed, looks to be female and not male. (Note the wide hips and large birth canal-like hole.) Also in the Next season's "When She Was Bad," they have another shot of the same skeleton, however the hips are much smaller and more male. (00:43:55)
Plot hole: Willow hacks into The Initiative's computer system and discovers air ducts and electrical conduits leading to Adam behind 314, but the room doesn't show up on the schematic. It seems unlikely that nobody who didn't know about Adam would have noticed this and investigated.
Revealing mistake: When Spike, Xander, Anya and the Buffybot are attacked by vampires in the cemetery, the grass for the cemetery moves underneath the vampires' feet as if it were a carpet. The cemetery was a sound stage and not an actual cemetery.
Other mistake: At the end the library that was rigged with explosives blows up. But the school's main entrance and the clock tower blow up as well, even though they are not rigged with explosives.
I Only Have Eyes For You - S2-E19
Continuity mistake: When George shoots Mrs. Frank, her body falls off the balcony headfirst on a closeup shot. She flips in the air once on her way down. But in the following wide shot, she flips in the air on her way down again.
Storyteller - S7-E16
Continuity mistake: There is a shot where a girl is turning invisible, and when the camera switches to Buffy slapping her, she is fully visible, until it turns back and she is slowly becoming visible again.
Revealing mistake: When the Gentlemen are chasing Tara in Stevenson Hall, in the first hallway two Gentlemen are floating down the corridor and you can tell they're on wires because the one on the screen's left "jumps" a little as if his wires got snagged.
Chosen answer: Angel is saying that he is still jealous and Buffy recognizes that this is his way of saying he wishes that they could be together. That is why they both smile.