Bill: laughs it’s funny how dumb these ponies are!  
Sweetie: Uhh? Ms. Shores? your headdress is talking.  
Sapphire: huh? looks up to see Bill  
Bill: Hi!  
Sapphire: Who and what are you?  
Bill: Name’s Bill Cipher.  
Rarity: You look like a tacky pyramid with an unfashionable hat and bow tie.  
Bill: says you!

Bill Cipher: Yellow Equestria. It’s good to finally be here. How are this going Rarity, Sweetie Belle, and Sapphire Shores?  
Rarity: How do you know our names?  
Sweetie Belle: I knew my sister was good but I didn’t know you were this good.  
Bill Cipher: Gemstone may be good Quaver, but she isn’t that good. Wouldn’t you agree, Dolphin?  
Sapphire Shores: I…I don’t…What are  
Bill Cipher:It seems that Dolphin’s brain is on the fritz at the moment and to answer you question Rarity I know things. Lots of things!  
Sweetie Belle: Rarity, hold me I’m scared.  
Rarity: I’m scared too Sweetie Belle.  
Luna: Get out of this filly’s mind dream demon!  
Sweetie Belle: Wait, so I am still dreaming?  
Bill Cipher: Right you are Quaver.  
Luna: Who sent you here Isosceles Monster?  
Bill Cipher: Pearls sent me here Eclipse, but I’m not here to fight with you just for some torment. Later days, tell Sunspot I said high. Remember Quaver! Cutie Marks are an illusion, the world is fictional, change your oil regularly, bye!

I can hear his voice
 
That’s normal, right?

Every time I see this I hear the extremely distressing blast of sound the Martian Tripods make in the (criminally underrated) Tom Cruise version of War Of The Worlds.