“Hey, Celestabellebethabelle. You make a nice wall-mounting.”
 
“What?! Mabel?! How did you…?”
 
“I had a little help from another unicorn.”
 
“Actually, I’m an alicorn, Mabel, but that’s a common mistake people make. Those two terms sound so similar, honestly.”
 
“Who…who are you?!”
 
“Name’s Twilight Sparkle. Mabel told me how much of a jerk you were to her, so I used some Equestrian magic to turn you into a living mounted head.”
 
“If I ever get out of this, I’m going to—OUCH! What was that?”
 
“Oh, I just cut off some of your hair for Mabel. It was her hair you needed, right?”
 
“Yeah, Twilight. It was.”
 
“Oh, and you aren’t getting out of there. Mabel told me those horns of yours can only glow, point towards the nearest rainbow, or, my personal favorite…”
 
(Twilight hands Mabel a remote with a button on it. She clicks it, and rave music starts playing from Celestabellebethabelle’s horn.)
 
“…play rave music.”
 
(Mabel clicks the button again, and the music turns off.)
 
“This is what you get for being a jerk, you know.”
 
(Mabel and Twilight fist-bump, then grab the Unicorn mount and put it in a box marked “Express Shipment To The Mystery Shack”. Twilight magically removes Celestabellebethabelle’s mouth before putting her in the package and throwing it into a mailtruck passing by.)

@Dirty Bit  
COMPLETELY AGREED !!!
 
Go that gave a bad name to the unicorns, do you remember what they said about the horn? …
 
(seriously, that made me laugh)

She deserved it; that pony was a jerk.