Continuity mistake: When Angel grabs Cordelia's hand as she apologies after telling him to "get over it", the position of Angel's hand changes between shots.
Disharmony - S2-E17
Continuity mistake: In some of the shots in the scene with the red bird, it is raining and in some shots it is not.
Continuity mistake: When Lorne covertly warns Angel that the hotel is bugged, he places a note in Angel's pocket with his hand on Angel's shoulder. When Wolfram and Hart watch the video feed later, the hand that was on Angel's shoulder is now in front of Angel's chest. (00:22:50 - 00:37:00)
Carpe Noctem - S3-E4
Continuity mistake: When the gang rescues Angel and returns him to his normal form towards the end of the episode, Cordelia shocks him unconscious with a taser and he falls to the floor, lying on his front. But when Fred whacks him on the head with her baseball bat, he is suddenly lying on his back.
Continuity mistake: When Wesley is explaining that Angel feels like he doesn't belong in the world, the amount of donut he's holding changes. (00:13:30)
Smile Time - S5-E14
Continuity mistake: Angel is coming down the hall in the Smile Time set and he sees the trash man walking past him. In the behind shot, Angel is farther back, but when it shows the side and front shot, he's right behind him.
Continuity mistake: When Wesley tells Faith that Angelus is back, she says, "Step away from the glass" and hangs up the phone. When Wesley jumps from his chair (to allow Faith to smash through the glass and escape) you can see Faith behind the glass with her hands up to her face and standing, but in the close up of Faith her hands are at her sides and she is only just getting out of her chair. (00:23:20)
Continuity mistake: When Fred is running from the oncoming white car, she runs toward a blue car getting fixed on the side of the road, but jumps out of the way as the white car hits the blue car. Fred hits the ground and rolls over to the fence, but in a following shot it shows Fred only just hitting the ground and she is on the grass, not next to the fence. (00:14:20)
Continuity mistake: When Jasmine picks up the car and throws it at Angel, it cuts to a shot of Angel moving out of the way then shows the car falling from the bridge. First mistake, Jasmine disappears from the shot when the car is falling, and second, the car falls directly straight and at a higher point than Jasmine actually threw it. (00:35:50)
Blood Money - S2-E12
Continuity mistake: During the charity event when it shows the birth year and death year of Holland Manners, it suggests he was 49 years old when he died. But in an earlier episode, he attempted to sacrifice his daughter for his 50th birthday.
Continuity mistake: When Angel and the others infect Connor with Cordy's blood, Gunn rips open Connor's shirt. In the following shots, the shirt closes and then opens again. (00:41:40)
Disharmony - S2-E17
Continuity mistake: When Angel pulls Cordelia aside and says that Harmony cannot work with them, a man in the background walks past in the shot of Cordelia but we never see him walk past in the shot of Angel.
Continuity mistake: When the demon Angel and Groo are chasing crashes through a wall, the resulting hole lets in enough sunlight to force Angel into the shadows. A few shots later, Wesley notices Angel standing in the entrance to the hole. Only a few moments have passed, so Angel shouldn't be able to stand where he is. (00:15:20 - 00:16:20)
Answer: Everybody including Angel saw her. After helping them and then being left alone to talk to Angel, Cordelia says that the Powers That Be let her come back one more time to help them. After Angel gets a call saying that she died, he realises that it was her spirit that was helping them the entire time.