Firecracker watched the pegasus disappear behind a tree to their left, and reappear a moment later from behind one on the right, smiling. She approached them, still smiling, and sat down besides them.
"Fun stuff," they commented. "Isn't it dangerous?"
The mare shrugged. "Only if I'm not careful with where I pop back out. I don't know what would happen if I did exit where something else is, but I'm happy not knowing." She swayed from side to side. "It's easier out here. The trees stand out more on the other side. Buildings are a lot harder to avoid."
Firecracker nodded. "I see. What does it look like, on the other side, exactly?"
"It's... different." The made pursed her lips, thinking. "I can't really put it into words. You'd need to see it yourself to understand. It's like..." She trailed off, and her hoof trailed on the snow in front of her. "Imagine you were a flat shape, on a flat world, and suddenly one day something picked you off from that world and left you to drift around in space. And imagine you saw the world, your world, and realised its shape in space is curved. That's what it's like."
Firecracker quirked an eyebrow, intrigued. "And what shape is our world, in the one above?"
The mare shook her head, her blonde mane swishing from side to side. "I have no idea. I don't think I can even comprehend it. I'm still thinking in three dimensions, even when I move in four. But I can see shortcuts. Like a shape might see that a line between two points of a solid is shorter if it passes through it and not along the edges, without understanding that the solid is a cube or a sphere or a cone."
Firecracker nodded again. "I understand." They remained silent for a moment. "Can you show me? Take me with you on the other side?"
Again, the grey pegasus shook her head. "I've thought about bringing others with me. I don't know if I can, and I don't want to risk it. If I bring you in and lose you, I might never be able to find you again. And I don't even know if you'd be able to be there at all."
Firecracker swallowed, a bit disappointed. "How fast is it?"
The mare looked at them, a smile slowly spreading on her lips. She blinked out of existence before they had a chance to say anything else. And a few seconds later she reappeared, holding a postcard. She passed it to Firecracker, who looked at it and saw it was from Appleloosa. "That fast," she replied. "If I want it to."
Firecracker blinked, very clearly impressed. "Not bad at all. Princess Twilight must love having you around."
The mare chuckled. "I think she hates it, actually. One more thing she can't figure out."
Firecracker chuckled as well. "I don't think you've told me your name yet."
"You haven't either."
The pegasus sighed. "True enough. I'm Firecracker. What about you?"