took me a good second to get what was going on… maybe something else to indicate which one’s the real Twilight Sparkle

And Rape Tentacle Beast said “You think you can stop Rape Tentacle Beast?”,  
And Princess Twilight was all “No, I shall become the Rape Tentacle Beast”,  
and then Twilight was Rape Tentacle Beast.

Then the tentacle beast in Twilight’s body runs away to Ponyville, and hilarity ensues.