To get the effect of Lorne's detached head, Andy Hallett's body was digitally removed from many scenes. In other situations, an animatronic radio-controlled head was used.
The Groosalugg says that Cordelia, as a human, is not meant to have the visions, reiterating what Wesley and Angel said. As a half-demon, Doyle could cope with the visions, but as a human, Cordelia is becoming increasingly sick as a result of the visions.
When Cordelia originally received the power to have visions from Doyle, she tried to pass them on to anyone available, including Wesley when he first arrived in Los Angeles. In spite of, or perhaps because of, having experienced the pain and emotional suffering of the victims she has seen in her visions, by this episode she refuses to give up the power, describing it as "an honour."
It is established that Lorne, as a Pylean, has 3 toes and can survive having his head removed as long as his body isn't mutilated. In contrast, Silas and his species of demons cannot survive without their heads, something the rebels confirmed.
Willow's hair is straight in this episode, changing from the usual curled/wavy style that she wears through the majority of Season 5 of Buffy the Vampire Slayer (1997).