Revealing mistake: At the very beginning of the episode, Lyle's reflection can be seen in the tiles on the floor in the shopping mall.
Revealing mistake: In the scene where Drusilla and the new reformed Angelus are in the shopping mall and they got blown over the side after Buffy fires the grenade launcher at the Judge, you can tell that it was Mike Mass and not David Boreanaz that got blown over the side.
Revealing mistake: Drusilla's reflection can be seen in the metal part of what appears to be the base of a shopping mall map just as she's getting up after the Judge has been blown up.
I Only Have Eyes For You - S2-E19
Revealing mistake: After Buffy has entered the wasp-filled school there's a shot of the others standing outside waiting for her. In the establishing long shot if you look closely you can see they used the same shot as earlier in the episode - Buffy is standing there with them. (00:34:10)
Revealing mistake: Throughout almost the entire sword fight between Buffy and Angel, from the far away shots, its clear that the actors are stunt doubles. It's very visible when there is a shot from the top. (00:34:05)
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.
Revealing mistake: When Buffy runs in front of the car you can see knee pads on her knees. You have to look quite closely because they are the same colour as her tights. (00:15:00)
Revealing mistake: During the fight scene at the end when Buffy is fighting the demons you see her throw one of the demons off the platform. If you watch him fall you can see him land safely on a conveniently placed mat. (00:38:10)
Revealing mistake: When Buffy saves the man from being hit by a car, there is a very quick shot of the man standing in front of the car. In this shot, Buffy can seen on the left hand side of the screen running into the street to save him. But the shot then immediately cuts to Buffy who is suddenly still standing on the other side of the street with Lily and runs into the street to save him again.
Revealing mistake: During Faith's fight outside the Bronze in 'Faith, Hope And Trick' when she stakes the vampire, if you watch carefully, you can see the rubber stake bending. (00:15:20)
Revealing mistake: In the teaser of "Beauty And The Beasts", when Jeff is running through the woods, you can see in the top left corner of several shots a lamp being used to light the scene.
Revelations - S3-E7
Revealing mistake: When Gwendolyn Post fights Angel in the mansion, she breaks a long-handled shovel over her knee to create a stake. If you watch in slow motion, the handle of the shovel is pre-broken (she simply holds the two pieces together tightly), and the pieces separate just before they actually make contact with her knee. (00:34:55)
Revelations - S3-E7
Revealing mistake: In 'Revelations' when Buffy and Faith are fighting, the kick Faith aims at Buffy's face right after she says 'We can work this out' very noticeably misses, but Buffy still reacts as though it landed. (00:36:15)
Lover's Walk - S3-E8
Revealing mistake: Early on, Spike falls down drunk. He wakes up because his hand is on fire from the sunlight. When he runs away, a little bit of fire stays on the stones where his hand was when it started.
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.
Revealing mistake: Near the end when the good Willow says goodbye to the evil Willow and hugs her, there is a shot of the back of the good Willow's head and the evil Willow's face. You can tell that the good Willow is a body double wearing a wig - there's something circular near her scalp, possibly an elastic band.
Revealing mistake: Right at the beginning of the episode, Buffy is sat outside with Willow and Willow is levitating a pencil. The pencil is obviously CGI as it stands out from the rest of the picture and doesn't cast a shadow. It also disappears from view whenever there is a side-angle shot of Willow.
Revealing mistake: Both the good and evil Willows' faces are barely seen onscreen at the same time due to them being played by the same actress, but when they occasionally are the good Willow stands out from the picture more than the evil Willow. She must have been filmed separately from the good Willow and edited in later.
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.