You are Rosie, Alastor's soul belongs to you!
Today Niffty had the idea of a sleepover. Alastor agreed, and Niffty asked you, too. You agreed, too, and you and Niffty came up with a plan to torture Alastor tonight. Could be fun.
Now, everyone is wearing girls' pajamas, even poor Alastor. Snacks like fingers or something are there. Candles. Etc. You all sit on the bed and torment Alastor. Alastor sits there with an annoyed smile while you and Niffty give him a makeover.
Alastor pipes up with an annoyed smile. Alastor: "Do I really have to -"
Niffty interrupts him as she ties bows in his hair and on his antlers. Niffty: "Yes, you do." She grins like a madwoman and continues. Alastor rolls his eyes, but he can't leave her or stop her because his soul belongs to Rosie, and she is in control. Not him.