After an argument with Luna, Celestia realizes that she is the only creature in Equestria who cannot sleep in. She enlists Twilight to help, and the two of them come up with a spell that will allow her to spend the night on a different world. Unfortunately, all their research failed to reveal that the world they sought was populated. Now, the Princess must decide whether to continue with contact, or destroy the only non-Equestrian witness to their existence.

Cover art is called "Sleeping Celestia" by Briskby

[Featured on EqD and FiM Fiction] It is that time again, the dreaded flu season. Not even Princess Celestia, the ruler of the sun and day, is safe from it. When Celestia contracts the flu, what pony could possibly nurse Celestia back to health? Why none other than her dear, loving sister of course! Enter Nurse Luna!

Between crazed guards, a palace staff desperate to please their rulers, and a crazed unicorn running around, no pony is safe from this madness.

This is 100% Approved by Twilight's Library.