Continuity mistake: After Buffy decides not to take the antidote to the demon's venom, we cut to a scene at the mental institution. She says she wants to go home with her mum and dad. As she says this her dad puts his hand on Joyce's left arm. In the following shot, Joyce suddenly has her right hand on top of his when it wasn't in the previous shot.
Factual error: After Buffy drags Xander down to the basement she locks the door and goes upstairs to find Dawn. When she locks the basement door, the handle is on the left side of the door and she turns the key to the right. In reality, a door with the handle on the left needs the key to be turned to the left to lock it. So Buffy did in fact unlock the door, not lock it.
Continuity mistake: In the basement, immediately after Buffy pulls her hand out of the demon's chest, her fist is completely dry. Two shots later, it is covered in gooey demon fluid. (00:40:35)
Revealing mistake: Right at the beginning of the episode just before we see Warren squirt Jonathan with water, we see Buffy on one of their security cameras. The footage of her is pre-recorded as the progress bar for QuickTime Media Player is visible at the bottom of the screen. The window was moved down to hide this fact, but not far down enough to hide it completely.
Continuity mistake: After Buffy decides not to take the antidote to the demon's venom, we cut to a scene at the mental institution. The doctor talks to her about ridding her mind of the things that support her "hallucinations". As he talks to her about this, the position of his hands change from pressed together in front of him to in his pockets between shots.
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.