Other mistake: After Gage turns into a monster and fights Buffy, the two monsters slide into an open grate. During the shot, there's some sort of weird "glitch" in the background where the garbage can and wall seem to slightly move. All I can assume is that a few frames were trimmed to speed up the shot and it may have exaggerated subtle camera movement, making the background appear to "jump" slightly.
Continuity mistake: When Buffy, Willow, and Cordy are talking at the swim meet (after Gage waves at Buffy), the way Buffy is holding her hands changes back and forth between two positions as it cuts between her and Cordy. Seems two different takes were used, and she had her hands in slightly different positions in them.
Continuity mistake: When Angelus is spitting out Gage's blood, he goes from straight up to leaned over between cuts.
Continuity mistake: After Willow says that the student was killed by being opened up like an Oreo "except without the chocolaty cookie goodness," Buffy's hands go from together to apart instantly between cuts. She then puts her hands back together only for them to be apart again in the next shot.
Continuity mistake: When Buffy is talking to Cameron in his car near the start, the amount of light on Cameron's face coming through the windshield changes between cuts a few times. Sometimes the top is up over his eyes, sometimes it's down by his nose, etc. Also, depending on the angle, sometimes there's a purple glow on his face and sometimes not.
Continuity mistake: When Buffy and the guy are talking at the beach in the beginning, right before they hear a voice scream "Somebody help me!", the guy starts to turn to look at the tide. However, in the next shot, he's instantly facing Buffy again and then turns to face the tide a second time.
Continuity mistake: When Buffy's mom sets down the carton of orange juice on the table after the golf trip, watch closely. The continuity is nightmarish. The carton rotates multiple times between cuts. The cap is on, then off, then back on again between cuts. And Buffy's mom's hand keeps moving on and off the carton between cuts.
Continuity mistake: After the mini-golf scene, Buffy comes down to her kitchen. Her mother greets her and sets down a carton of orange juice. In the first shot, her mother is holding the carton with both hands. But in the next shot as she sets it down, she only has one hand on the carton.
Continuity mistake: When Buffy, Xander and Willow are talking at the school near the beginning in front of the vending machine, watch the way Buffy is holding her pink binder. First she's holding it to her side, but shifts it in front of her chest. Instantly, in the next shot it's back by her side. Then it's back in front of her chest again.
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.