Continuity mistake: Timothy is wearing disposable gloves as he is training Buffy at the grill, but in the shot when he puts the raw patties on the grill, he is barehanded. (00:16:15)
Continuity mistake: In 'This Year's Girl' when Faith is taunting Joyce with all Buffy's uncollected mail she flings the envelopes across the bed one by one, scattering them. When Faith is fighting Buffy later on they are all in a pile again. (00:37:20 - 00:38:40)
Continuity mistake: In the episode 'Anne' when the latest people to be brought into hell are lined up with a demon talking to them, there are 3 or 4 people standing between Buffy and Lily. When the demon asks them all in turn 'Who are you?' we see him asking Lily and after that the shot rests on Buffy, but in the background we only hear him ask one more person before he gets to Buffy. (00:35:50)
Continuity mistake: In 'The Initiative', Riley, Graham and Forrest are looking in through the windows of Stevenson Hall with thermal goggles looking for Spike, they see him walking towards Willow. When we see Willow and Spike seconds later he is still sitting on the bed where he was for most of the scene. (00:37:30)
Visible crew/equipment: When Xander is in the bathroom after Buffy called him to look for the talisman, he bends down and grabs the talisman that lays under the sinks. As he stands the camera pans up to the mirrors and on the left side you can see the reflection of a crew member crouching over the hole to the old school. It's not the female manifest spirit as the clothes are wrong and she then appears from a different part of the room.
Continuity mistake: After the 'hell hogs' interrupt the ritual, Xander pulls Willow out of the way. He then tells Anya and Tara to "take off." which they appear to do, starting to run Into The Woods. But then in the next shot, they are back standing still in the clearing (on the left of the shot).
Continuity mistake: When they ask about the demon that Xander and Cordelia encountered in Buffy's basement, Xander points to the bug that Cordelia threw from her hair onto the open book. He then slams it shut. A shot later, the book is gone.
Continuity mistake: When Buffy wakes up she is wearing metallic nail polish, yet when she went to sleep previously, she has no nail polish on. Later in a scene where Buffy is dreaming about her night with Angel she has the nail polish on again, even though that took place the night before when she did not have her nails painted. (00:01:15)
The Dark Age - S2-E8
Continuity mistake: Cordelia tells the Scoobies that Giles was talking to the police about a homicide, but this wasn't mentioned in the time that she was in the room. (00:18:15)
Seeing Red - S6-E19
Continuity mistake: At the beginning of the episode, Buffy is running from the large saws and jumps out the door, she sits up and you can see the book is fully intact and in one piece. After the opening credits Tara picks up the same book and it falls apart from being cut in half.
Once More, With Feeling - S6-E7
Audio problem: During Buffy's first song she does a spinning kick to a vampire's face as she sings, "I've been making shows of trading blows, just hoping no one knows." But as she spins, her lips are not moving.
Revealing mistake: One of the arrows that Spike gets hit with passes through just below his left shoulder, but there are times when you can tell that it is a fake arrow because the part of the arrow sticking out at the front moves and the part at the back does not. Look at the arrow just after Buffy turns Hus into a bear.
Continuity mistake: When Willow catches Xander and Cordelia kissing in the library, the hair next to Willow's right ear moves between shots as her and Xander are talking in the hallway.
Storyteller - S7-E16
Visible crew/equipment: During Andrew's fantasy of him, Warren and Jonathan being Gods, something dark is reflected in of the piles of gold. Possibly a camera or camera crew.
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.
Visible crew/equipment: When Buffy and Dawn are at the top of the metal tower, and Buffy is still very dazed from being called back, there is an overhead shot with a piece of the tower falling down; if you look left of the falling piece, you can see a guy wearing a hard hat walking about.
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.