Ground State - S4-E2
Factual error: In the flashback to Gwen as a child in 1985, she is dressed in a jacket tagged with an "Old Navy" zipper. That clothing store chain wasn't founded until 1994.
Angel (1999)
1 factual error in season 4
Continuity mistake: Right after Cordelia has her vision, Wesley goes to the whiteboard. In the "Case" column he writes "N.D.U.O." Underneath what looks like "CARYNSS" crossed out. But once they find out that it is a Prio Motu demon and Angel writes it on the whiteboard, "N.D.U.O." disappears even though Angel did not rub it off.
More quotes from Angel
Trivia: In the opening credits there is a shot of a girl standing alone on the corner of a street. This was taken from the Buffy episode "Anne", when Buffy was staying in Los Angeles.
More questions & answers from Angel
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.