"The thing about Buffy and Spike is they understand each other on a level that nobody else does. They've both lived a hundred lives and I think there's a connection there that we will see evolve over the next couple of years where she realizes that he really is someone that she can trust, someone that's a companion to her and someone that really understands her unlike anybody else."
Sarah Michelle Geller

Spike is something special. Spike retained enough compassion. Some part of his soul is still was always there that allowed him to fall in love with Buffy where no vampire could.
David Fury

As an actor, I right away played an attraction to Buffy, even though Spike was fully in love with Drusilla. There was a scene, my very first day of shooting, where I was hunting Buffy, not to fight with her, but just to observe her and see what her fighting style was. And I'm looking at her in the Bronze and I'm kind of walking through the crowd, watching her dance, and there was something both very much of a hunter, "I'm going to kill you", but there's also heavy sexual undercurrent, and that just came off the day (laughs) watching Sarah dance, really. But, you know, Spike was the perfect boyfriend, so he would never go beyond that. But there was that attraction immediately, and by the time we get to Season 4, it's developing. There are two episodes where the characters get together. One is kind of a what-if episode which is brought on by a spell that Willow casts which is completely unreal. But then there's a scene later on in the season where Faith takes over Buffy's body and just messes with Spike's mind. And there we see for the first time that if Spike would have gone for it, he would very much like to have kissed Buffy. And that's why he can't kill her, because he's in love with someone who's truly good. And so he's going to try and be the kind of man that Buffy would like to have.
James Marsters

"I think it's good to have Spike and Dawn together, because it shows Spike's mindset. Which is that anyone who Buffy loves is very important. So, he will protect anyone Buffy loves. Don't hurt Buffy. Don't hurt anyone that's important to her. Keep them safe."
James Marsters