When the vampires enter the Bronze, one of them throws a patron into a table, breaking it. A moment later, when that vampire is talking at the people in the club, the previously-broken table is back in place, cups and all.
At 14:40 we see a couple, in red sleeveless jackets, leaving the movie theater behind Vampire Willow. They take several steps into the street before the view cuts to a closer view of Willow. We then see them emerging from the theater again.
At 15:25, as Vampire Willow is entering the Bronze, behind her you can see a guy reach out and pull the door closed behind her. The view then cuts to a wider shot and the door is suddenly open again, with the same guy pulling it closed in the same way a second time.
When the vampires first take over the Bronze, vampire Willow selects and bites a frightened patron, Sandy, in the neck. When Willow releases Sandy to fall to the floor, Sandy's uninjured neck is briefly visible.
At 19:31, as Vampire Willow says, "Get your friends..." the view cuts from a wide shot to a close-up of her face during the word "friends." In the wide shot, however, her lips are not moving. (Her voice in the wide shot is lapped back from the close-up; she was not speaking the line in the wide shot.)
At 14:40, as Vampire Willow is walking down Main Street, in the sky behind her you can see light reflecting off the platform of the mobile lighting tower that is illuminating the scene.
There are two cases of consequence-free living in this episode: first, Wesley arrested Faith in the previous episode, and Faith escaped by threatening to kill one of his people, but now they're working together on the slayer skills test as if none of that had happened. Second, Vampire Willow kills someone at the Bronze in front of dozens of witnesses, but this somehow causes regular Willow no legal problems; even if the police had accepted the "that was actually my evil twin from another dimension" defense, Willow would still have had to answer for aiding in a fugitive's flight (back to that dimension).
Anya tells Willow "I heard you were a powerful Wicca," the first of numerous times in which the term is misused. Wicca is a religion, and someone who practices the religious is Wiccan.
It takes at least a day normally for victims turned vampire to "rise" on this show. Buffy and Xander have seen human Willow alive and well not a couple hours before encountering vampire Willow yet they don't even mention how she could have been killed and already risen in that short amount of time.