I think it's vowels.
You are in a strange land called Freeland, and there is only one Law here. There is a mirror, but no reflection; there is pizza with cheese, but not sausage; there is pepper, but no salt; there is door, yet no entrance or exit. What is the Law?
An odd day is one which has both its day and month odd for instance 13:5:2000. How many odd days are there in the year?
Here on Earth it's always true, that a day follows a day. But there is a place where yesterday always follows today! What is it?
I may seem real but it always turns out I was never there in the first place… you only see me during a certain resting stage. What am I ??