When he auditioned for Spike he had his natural hair colour (brown) and TPTB worried it may be too close to Angel's. But in the end James won the role on his performing ability alone and Spike was born. Originally the role was meant to be short lived, he and Drusilla were to be the Sid and Nancy of the vampire world, but the fans loved the character so much that he has turned up like a bad penny again and again.
James On Spike
"It doesn't hurt to be known as cool sexy killer guy."
"The mask makes me scary and Joss' words make me funny, and that's all there really has to be."
"I love playing Spike because I get into fights and no one has to go to the police station and no one has to go to the hospital."
"I never in a million years thought, 'Hey,
"One of the components of Spike that I miss, is the romance."
"It's really important to stop trying to kill Buffy, because if he keeps doing that, he's either going to be killed himself or he's going to become pathetic in failing so many times. That was my worry. I didn't see how they were going to fit me in."