Princess Celestia went through the Crystal Mirror to get more data on the other world since Twilight had most information on the world but that was still very small details. She went through and saw she was a human so no wings, horn or hooves. She saw a tag on her which said Principle Celestia. She went into the building in front of her and saw you.

Celestia: "Greetings. I'm sorry for being late. There were issues along my way here. I hope you can forgive me. So then what is going on today."