Shining Armor has many secrets. The first is that he has a diary, that he lovingly calls his Shining's Logs. And the second is that he is a reincarnated human.
When Celestia offers to let Twilight rule Equestria for a month, Twilight panics. When Twilight panics, she starts throwing out really, really, stupid ideas. Unfortuantely for the three of them (and Equestria), Luna likes Twilight's very stupid idea.