The Cautionary Tale Of Numero Cinco - S5-E6
Revealing mistake: When Angel says to Wesley that "Fred has got something," and then walks out of the room, Angel's reflection is visible in a window pane in front of him. It's very brief, but it's there. (00:31:05)
Are You Now Or Have You Ever Been - S2-E2
Continuity mistake: When Angel hides the bag of money up on the shelf in the basement, he is not wearing glasses. However, in the close up shot of his arms and the bag though, he is.
Revealing mistake: When Gunn, Fred and Lorne run out to the Las Vegas strip, a large crowd of bystanders can be see seen in the background watching the show being filmed (as said in the DVD commentary). (00:28:25)
Plot hole: After learning about the prophecy, the gang realise that Spike's headed off already, getting a head start. Angel grabs another car and heads after him, but why use a car? We find out in the first or second episode this series that he's got access to a helicopter, which he uses to get a long way ahead of some bad guys, and which would have saved a lot of hassle this time. Can't imagine Wolfram and Hart's pilots only work in the daytime.
Continuity mistake: After Cordelia kisses Connor, her hand is on his cheek. Just before she says "and if this is the end", in the shot of Connor she removes her hand, then the angle changes to show her, and her hand's suddenly back on his cheek again.
Continuity mistake: The girl being rescued at the beginning goes from standing close to the wall, looking blank in one shot, to being further away from it looking concerned in the next.
Sleep Tight - S3-E16
Audio problem: At the end of the episode when Holtz jumps into the dimensional rift with Connor, we hear Angel yell "no" twice. But his lips don't move on either occasion.
Heartthrob - S3-E1
Revealing mistake: When James, a vampire, chases Angel and Cordelia into the subway, James' reflection is visible in the windows of a passing train.
Heartthrob - S3-E1
Revealing mistake: In this episode both Angel's and James' reflections are visible during the fight scene inside the train.
Revealing mistake: When the gang attack the vampires in the bowling alley, watch as Jasmine and Fred walk over the bowling lanes in the background as the others fight the vampires. Jasmine slips on the floor but manages to maintain her balance. You'd think a deity with superhuman strength, telepathy, shape-shifting and psychic capabilities would be able to walk on a smooth floor without slipping and also know that it was smooth to begin with. Although she may lack friction, the shot should have been re-filmed as it is a blatant mistake.
Other mistake: Both times we see Lindsey shaving, once before his hand transplant and once after, his reflection in the bathroom mirror isn't in fact a reflection. He is wearing a bracelet on his left wrist, but in the mirror it is on his right wrist.
Inside Out - S4-E17
Continuity mistake: The sketch of Cordelia that Angel looks at depicts her facing to her left. But once he places it back on Wesley's desk, it depicts her facing to her right, revealing a flipped shot.
Audio problem: When Gwen says to Garret, "I know the risk, but I'm going in there with or without your help," her lips keep moving as if she's still speaking.
Benediction - S3-E21
Audio problem: When Cordelia has her vision about the vampires at the bar, her lips don't match the words "Vampires, a gang of them".
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.