CAPTAIN PEROXIDE. Buffyverse Term/Concept/Idea/Intratext.
As a designation for bleached-blonde, "Billy Idol wannabe" ("Sleeper") Spike, the name "Captain Peroxide" is first used by Xander in "Smashed":
(the phone rings, Buffy answers) Hello, Magic Box.
SPIKE: Slayer.
BUFFY: Spike?
SPIKE: Meet me at the cemetery. Twenty minutes. Come alone.
BUFFY: Spike?
SPIKE: (rolls eyes, mutters) Bloody hell. Yes, it's me.
BUFFY: You're ... calling me on the phone?
SPIKE: Just be there.
BUFFY: Why? Are you ... helping again? (Buffy speaks louder for Xander & Anya's benefit) You have a lead on this frost monster thingie?
SPIKE: Something like that, yeah. Thought you might be up for a little grunt work.
BUFFY: What?! No, (whispers) no-no grunting!
SPIKE: (grins) I was talking shop, luv, but if you got other ideas ... you, me, cozy little tomb with a view...
(she hangs up on him)
XANDER: So, what did Captain Peroxide want?
BUFFY: Nothing! (nervous) You know, he just, you know, wanted to see if I-I wanted to patrol, for, for the, the monster. But I, I told him that I ... would ... not.
Independently Angel use the same moniker for his rival-for-Buffy's-affections in "Chosen":
BUFFY: If I lose— if this thing gets past Sunnydale— then it’s days, maybe hours, before the rest of the world goes. I need a second front and I need you to run it.
ANGEL: Okay. That’s one reason. What’s the other?
BUFFY: There is no other.
ANGEL: Is it Spike? You’re not telling me something and his scent… I remember it pretty well.
BUFFY: You vampires. Didn’t anybody ever tell you the whole “smelling people” thing’s a little gross?
ANGEL: Is he your boyfriend?
BUFFY: Is that your business?
ANGEL: Are you in love with him? (beat) Okay, maybe I’m out of line but this is kind of a curve ball for me. I mean, we are talking about Spike here.
BUFFY: It’s different. He’s different. He has a soul now.
ANGEL: Oh. Well.
BUFFY: What?
ANGEL: That’s great. (sotto) Everyone’s got a soul now.
BUFFY: He’ll make a difference.
ANGEL: You know, I started it. The whole having a soul. Before it was all the cool new thing.
BUFFY: Oh, my god, are you twelve?
ANGEL: I’m getting the brush-off for Captain Peroxide. It doesn’t necessarily bring out the champion in me.
BUFFY: You’re not getting the brush-off. Are you just going to come here and go all Dawson on me every time I have a boyfriend?