Spike was born as a human under the name William Pratt London, England to Anne Pratt and her husband.
- "What color is your hair? Radioactive?"
- — Angel
Spike has a punk look with bleached blond hair. He greatly resembled the punk rock singer Billy Idol — something the show later commented on in universe, where Buffy suggested Billy in fact stole Spike's look. 
During his life as a human, Spike's appearance was drastically different. Instead, Spike (named William Pratt) had unstyled medium brown hair and often wore glasses.  In the 1950s, Spike had black hair, though later opted to stick with the peroxide blond hair in the late 20th century.
- "We like to talk big, vampires do. "I'm going to destroy the world." Its just tough-guy talk. Struttin' round with your friends over a pint of blood. The truth is, I like this world. You've got dog racing, Manchester United, and you've got people... billions of people walking around like Happy Meals with legs. It's all right here. But then, someone comes along with a vision. With a real... passion for destruction. Angel could pull it off. Goodbye Piccadilly, farewell Leicester-bloody-Square. You know what I'm saying"
- — Spike, Buffy 2.22 – Becoming, Pt. 2
- "Say no more. Evil is still afoot. And I'm almost out of that nancy-boy hair-gel I like so much. Quickly, to the Angel-mobile, away"
- — Spike, Angel 1.03 – In The Dark