Continuity mistake: In the scene where Xander and Anya have had their "one more time" and are lying in the cellar bed talking, the shot is on Xander and he is speaking. When he finishes speaking Anya starts, but the camera stays focussed on him, however, you can see part of Anya's face in the shot and her mouth is not moving despite the fact she is talking.
Plot hole: Willow and Cordy disappear during a vampire attack. We later see that they spent the entire night hiding out in a closet, but wouldn't Buffy have gone looking for them once the vampires were gone? She knew they had run off somewhere (she mentions it to Giles when she gets a stake from the library). Instead she just goes home, leaving them still missing as far as anyone knows.
Continuity mistake: In the beginning of the show, Buffy has two necklaces on, one long and one short. However, when Buffy, as Joan, is telling everyone her plan to get away from the vampires, she only has the short necklace on. Then when she is outside, running from Spike, as Randy, both necklaces are back on.
Continuity mistake: Whenever we see the two Willows together in this episode we see that Vampire Willow is understandably very pale in comparison to the living Willow. However, in the library with Cordelia, when Vampire Willow says 'How about dinner?' her face is no longer pale.
Continuity mistake: When Buffy wakes up in the hospital bed you can you can see the black strap of her tank top underneath the gown. Then when she gets out of bed on walk to Faith, and it shows her walking through the hall you can see a white spaghetti top through the gown.
Visible crew/equipment: Just after Dawn says "I like the trailers", we fade to black/commercials, then up again. Keep a close eye on the left side of the screen - you can see what looks like someone's hand flash into frame for a second, despite Dawn being alone in the room - looks like the director's hand signalling action.
Continuity mistake: In every other episode it's seen in, room 314 is a room directly off a corridor, but in "The I In Team" Walsh walks through the door off the corridor, then there's another shot of her walking through a door. Where did the second door come from?