The Harsh Light Of Day - S4-E3
Continuity mistake: When Spike finally gets into the area where the gem is and Harmony follows him up there, he puts on that necklace thinking it's the gem. When he realizes Harmony has the gem it shows him taking off the necklace. It cuts to another shot and then shows him again with the necklace, but minus the charm.
The Harsh Light Of Day - S4-E3
Continuity mistake: When Spike pins Harmony to the wall, his hands change from flat against her to grasping her shoulders, depending on the angle. (00:12:00)
The Harsh Light Of Day - S4-E3
Continuity mistake: When Buffy catches Parker talking to another girl he stands up to leave and slings his backpack over one shoulder. In the next shot it's over both shoulders. (00:34:45)
The Harsh Light Of Day - S4-E3
Continuity mistake: When Spike and Harmony find the treasure room containing the Jewel or Ring of Amarah, after Spike stakes Harmony he removes the necklace he had on, but in the next shot he's wearing the necklace again.
The Harsh Light Of Day - S4-E3
Continuity mistake: When Spike is in the area where the gem is located, he walks to the right of entry hole, where he finds the gem. Then Harmony appears from the right side of the screen, where there's obviously no entrance.
The Harsh Light Of Day - S4-E3
Continuity mistake: When Buffy and Spike are fighting on campus during the day, Xander tries to help Buffy but Spike throws him against a lamppost. When he lands in the ground he falls completely on the grass on his side but if you look behind Spike in the next shot he lies half on and half on the grass on his front.
The Harsh Light Of Day - S4-E3
Continuity mistake: Right before Spike jabs Buffy in the face on the college's campus, there are a ton of people around. But after he jabs her in the face and they start fighting, all of the people are gone.
Chosen answer: He had larangitis and because of the shooting specifications they had to have him shoot the scene with a bad throat, they then re-recorded his lines and dubbed them. At various points during the scene and indeed the episode you can see him touch his throat or rub it.