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: 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: 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: Right before Holtz and his men arrive at the hotel, Angel arranges three of Connor's toys in his cot. One of them is a teddy bear which he places in the middle of the cot. But once Holtz and his men arrive, the teddy bear is suddenly at the far end of the cot resting on the pillow.
Factual error: Connor has been raised since he was a few months old by Holtz, a man with a British accent, in a dimension where there are no other humans. There is no possible way he could have an American accent, yet from the moment of his return he speaks with one.
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.)
Factual error: Spike suggests that Illyria and Drogyn play Crash Bandicoot. They appear to be playing on an original Xbox console. The episode was broadcast on May 12th 2004, meaning that the only Crash Bandicoot game they could possibly be playing would be The Wrath of Cortex which came out on April 5th 2002 in North America because every other Crash Bandicoot game that came out before that was only on the Sony PlayStation (with the exception of Crash Nitro Cart, but they're not playing that one). Both Illyria and Drogyn appear to be playing the game. However, The Wrath of Cortex was a single-player only game. They're not playing Crash Twinsanity (available for the Xbox) either as that didn't come out in North America until October 1st 2004 and it too was a single-player only game.