@punzil504  
With that kind of mental gymnastics I can see Bat Octavia sulking upside in the ceiling corner.
 
Vinyl: “I SAID YOU LOOKED BAT NOT FAT! B!A!T!”

Did you lose weight? Not that I’m saying you looked fat before…

@ArgentBanner  
good point!

@Twilight_Shimmer  
Yes, but we don’t want to kill the Octabat.

@ArgentBanner  
I thought it was American Fast Food?

She has come to devour all the tea and crumpets! Quick, I think British vampires are weak to Bovril.

Well Octavia always did say Vinyl was driving her batty! XD

@wildrook  
Vinyl: “Wait! Octavia’s mom is a Vampire Bat Pony? AND YOU KNEW!”  
Octavia’s Dad: “Yes that the truth, Leaving Questions that don’t need to be answered.”

…I don’t know why, but I’m under the impression that Octavia’s Mom may be involved.

Vinyl,she has been turned into Bat Pony and you better RUN……..!!!!!!!!!!!!

@Zaknel  
Vinyl Scratch has a white coat and red eyes (according to some) that she keeps hidden behind sunglasses. It was an easily leap from that to think “vampire”.

@Dark Tail  

Mmmm, maybe it’s the teeth, did you go to the dentist? Your teeth look very white and clean.

@Hopeful_Ink_Hoof  
Totally not because it was only then I realised I’d forgotten to draw it in…

@Background Pony #A710  
That is actually what Bob points out in the description on Deviantart:  

She looks so naked without her bow. xD

@Zaknel  
Pale, only ever seemed to be seen in dark shots, we needed a token vampire in the fandom and flutterbat didn’t exist yet. Take your pick.

I know what it is! She got rid of her bow-tie! Mystery solved.

@Zaknel  
There’s a fan comic called “Adapting to the Night” with that premise.  
There’s an older one called “MY Roommate is a Vampire.”

@Zaknel  
Maybe this will help.

@SinnerWhoKeepsTrying1978  
Well, the problem is that it’s only one such a work. We would need more for something so random as this.

@Zaknel  
No, that’s pretty much it. But, experience and observation have shown me that fan fictions can do a good job of conveying a theory.

@SinnerWhoKeepsTrying1978  
Anything else?

@Zaknel  
I seem to remember hearing a reading of a story on that order. Scribbler was the reader, if I remember correctly.

“Lost weight? You seem to be a bit lighter on your hooves today…”