Cordelia: Wait, I thought vampires couldn’t come in unless you invited them in.
Giles: Yes, but, uh, once you’ve invited them in, thereafter they’re, they’re always welcome.
Xander: Y’know, I think there may be a valuable lesson for you gals here about inviting strange men into your bedrooms.
Cordelia: Oh, God! I invited him in my car once. That means he can come into my car whenever he wants.
Xander: Yep, you’re doomed to havin’ to give him and his vamp pals a lift whenever they feel like it. And those guys never chip in for gas.
Buffy: Giles, there has to be some sort of spell to reverse the invitation, right? Like a barrier, a no shoes, no pulse, no service kind of thing?
Cordelia: Yeah, that works for a car, too?
Buffy the Vampire Slayer – Season 2, Episode 17 – “Passion”