Continuity mistake: When Gunn is talking to Wesley near the start of the episode, he mentions that he's tracked Lindsay down, and that he's been living under the name "Doyle", and holds out the lease of his apartment. There's a close-up of the lease a few seconds later, in which the name "Lindsay McDonald" can be seen.
Continuity mistake: After Wesley, Cordelia and Gunn sing "We Are The Champions" and Cordelia mentions tequila being evil, we see Wesley put aside some shot glasses. These glasses change position three times throughout the rest of the scene without anybody touching them.
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.
Continuity mistake: When Angel writes "Prio Motu" on the whiteboard and says that they need to find it and narrow it down to somewhere, Wesley says "I may be able to help us with that." In the immediate closeup of Angel, his stance has suddenly changed. In the previous shot he was standing with his arms straight down and his hands close together, but in the closeup they appear to be as though he has his hands on his hips.
Continuity mistake: In the scene where Angel has just returned and given Cordelia her necklace, watch Cordelia's hands; they keep changing position in each shot. In one shot she is trying to put the necklace on, in the next shot she appears to have given up and brings her hands down and bundles the necklace in her hand. Then when the shot changes to behind her, she is trying to fasten the necklace behind her neck again. This happens a few times during this scene.
Continuity mistake: In season three episode "Anne" of BTVS, The character "Anne" who later comes to season two of Angel running a youth shelter had a rather large red tattoo of half a heart on her arm. However, no trace of it is to be found when she is on Angel. Tattoo removal is a rather pricey procedure, and she seems to be tight on cash until she gets the two million. Even if W&H would have paid for the procedure, there would be some scarring or residual pigments for such a large tattoo. (It's definitely the same character - Anne says that she used to think vampires were cool, until she met one. That's a reference to her first appearance (as "Chanterelle"), in which she belonged to a vampire-loving cult.)