Revealing mistake: When Buffy is invisible and in the social office in "Gone", she is searching for the summer files, and you can see a thumb picking them up. (00:20:40)
Continuity mistake: In 'Gone', when invisible Buffy is typing on the social worker's keyboard the letter 'B' is pressed several times. When she prints what she's been typing seconds later it's revealed to be "All work and no play make Doris a dull girl", a phrase which contains no 'B's. (00:21:10)
Revealing mistake: When Buffy is at the desk of the social assistant you can see the white wire at the left of the keyboard. The white wire controls the fake keyboard: you can see the wire moving. (00:20:50)
Continuity mistake: In the kitchen scene Buffy takes the pizza out of the fridge and closes the door, but in the next shot the door is open and two shots later it's closed again.
Continuity mistake: After Doris from Social Services leaves Buffy's house and Spike leaves after her, he takes his lighter out of Buffy's pocket. But earlier in the episode when everyone was packing away all of Willow's magic stuff, Buffy finds Spike's lighter and puts it in one of the boxes.
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.