This is how Nightmare Moon convinces Twilight to join her goes in My Little Pony: The Revenge of Nightmare Moon.
[Nightmare Moon is waiting when Twilight appears]
Twilight Sparkle: Nightmare Moon.
[Nightmare Moon notices she has wings]
Nightmare Moon: Twilight. You're an alicorn princess?
Twilight Sparkle: Yes.
Nightmare Moon: I commend you on my escape.
Twilight Sparkle: I'm afraid the feeling isn't mutual.
[Twilight turns to walk away but Nightmare stops her]
Nightmare Moon: Oh, I should have known you were always the element bearer of magic.
Twilight Sparkle: Oh, I'm not doing this for you. I'm doing it for my friends. [hushed] Just between the two of us, it's mostly for you.
Nightmare Moon: What? You're not saying you're refusing?
Twilight Sparkle: Surprise?
Nightmare Moon: I am surprised that someone with your intellect does not see this 'friendship' is but a new form of imprisonment. Clearly you've had to abandon your true nature to stay in their good graces.
Twilight Sparkle: What?
Nightmare Moon: Oh, please, I've seen this before. But she was always weak minded. You are Princess Twilight, you are legend, you cannot fall into the same trap that claimed the Tantabus! Help me grow strong, and be rewarded with something greater than friendship. Freedom.
Nightmare Moon: Once I've brought eternal night, nothing would give me greater pleasure than to see their world under the beauty of darkness. Who better to do so than the Princess of Friendship herself? Join me, Twilight, and reclaim your greatness. Unless, of course, 'weak princess' is the role you've always wanted to play in this world.
[Twilight lets Nightmare's magic consume her and her eyes turn nebula blue]
Nightmare Moon: You're my friend, Twilight. Become my apprentice. Learn to use the darkness within your magic.
Twilight Sparkle: I will do whatever you say.
Nightmare Moon: Good.
Twilight Sparkle: Like when the Dazzlings used their magic.
Nightmare Moon: Yes?
Twilight Sparkle: I pledge myself to your teachings.
Nightmare Moon: Good. The night is strong with you. You will become a powerful friend to me. Henceforth, you shall be known as Nightmare Nova.
Twilight Sparkle: Thank you, my teacher.
[Twilight bows to Nightmare]