Yeah, but you could do it just as easily without the exclamation point - "Vamp Buffy" gets the point across just as well. I think it's just a cutesy/silly fandom thing that caught on.
I think the description like that, with or without the exclamation point, is like naming Barbie dolls - you've got Malibu Barbie, Babysitter Skipper, Vamp Buffy and Amnesia Spike.
Writing should feel easy, like a monkey driving a speed boat.