Twilight lowers her head. "Y-Y-Yes Teacher." She looks around behind her at you, with a look of apology on her face, as her innocent rosebud opens up and a few droppings pushes past, smelling of dandylions. You close your eyes and mouth as the dry pellets just rolls down off of your face, and land in a puddle of your sex juices, and Twiligths sex juices dribbles down your chest, belly, over your own sex, and joins your own.
Princess Celestia shudders, and releases another massive bomb of orgasmal juices, using her magic to send the arc splashing down on both Twilight and yourself. She leans back and pants in exhaustion. "Thank you my dear student. I do hope you learned this lesson in friendship. Why don't you let our volunteer here live with you as you learn more lessons from those books I gave you from my own, personal, collection."
Twilight blushes even harder, but slowly nods at her mentor's commanding suggestion. Celestia smiles, and then stands up, having finished her business. "Now, both of you, take some of the toilet paper, and clean my mess up. No magic, Twilight." Twilight had just started to start her magic, when she was told that it was forbidden. You and Twilight, with shaking hooves, start in on the task at cleaning Celestia's rump. The smell is not as strong, but there is a lot of wetness that quickly seeps through the thin toilet paper.
After several minutes, Celestia's rump is as clean as ever. "Thank you student, daughter. Now, remain in here until I have taken the Royal Guard away from here, before you make your exit. Have fun you two." She winks at the both of us, before making her exit. You take some of the toilet paper, and scoop up Twilights droppings, and then deposits them in the toilet, flushing afterwards.
Twilight looks up at you. "Um...thank you for the lesson on friendship. It is only fair, that I return the favor. I have studies a few ways. I can either do what you did, or there is also using my horn on your insides. Please, pick so that I can apply the skills from my studies."