(My interpretation of Vdrake77's Idol Hooves during the Canterlot wedding)
*Edits for the first two chapters kindly provided by Airy Words!
Idol Hooves, is the only changeling in the entire Equestrian Guard and has been proudly serving for over a decade( while disguised). His enlistment buddy and friend, Shining Armor, the current Captain of the Guard is finally taking the next step to officially becoming Princess Cadence' s personal guard, 24/7.
With most guard being reassigned to the wedding, Idol (by Luna's demand) is given the temporary assignment to Princess Luna's guard given the shortage of Night Guard.
Now, after another all-nighter looking for potential threats and with Idol's persistence, Luna finally agrees and turns in for the day. With Idol Hooves being the sole guard watching Luna's door, a promise was made that could ruin Eqauestria.
Princess Luna will get her well deserved rest, and nothing short of Princess Celestia herself will wake the deathly tired princess.