There doesn't seem to be anyone around
Twilight is in the bathroom stall, making grunting noises and stinky smells. She is straining very hard. Harder than usual and she didn't even eat much fiber this week. Usually it is in her breakfast bars but she bought a cheaper brand with less health benefits.
She grunts. "Oh just come out! Little seed present yourself and make manifest in my toilet your destiny!"
She strains her intestine muscles some more. "It would be really embarrassing for somepony to witness this." She thinks this but does not say it out loud to herself.
"Little poop, have no fear and I will feed you the dreams of my people." Twilight says that out loud.
Spike walks in. He heard that and has a weird look on his face. He doesn't really know why he walked into the girls bathroom anyway and it stinks really bad. But Spike giggles at what Twilight said because it was embarrassing for him to hear and her to say, with the majority of weight on her."
Twilight, why are you talking to your poop. This is weird and I would really rather not be here." He pinches his nose.
The potty mare grunts mightily. "Eureka!" Then she shuts her eyes and says, "Shut up. My poop's perfect."