Frank Castle: “…What’s this? Colorful ponies? Am I in the right place?”
 
Twilight: “Um, who are you?”
 
Frank Castle: “My name is Frank Castle, but they call me ‘The Punisher’.”
 
The main six: “The Punisher?”
 
Twilight: “Why do they call you ‘The Punisher’?”
 
Frank Castle: Unzips the gym bag and takes out an minigun with an shit load of ammo. “That’s why.”
 
Twilight: ‘Damn. This guy is seriously armed… He looks like he’s ready for war!’
 
Frank Castle: “Now tell me purple pony. …Where is the one called ‘Fluttershy’? She’s the one who hired me.”

A truly terrifying crossover.
 
Go and Google for Frank Castle, the Marvel Comics character who sometimes calls himself “The Punisher.” I’ll wait.
 
I suppose it could be done as black humor.