This episode last aired on Discovery Family on September 18, 2021 at 10:30 a.m.
The students at Twilight's School of Friendship are cramming for a "History of Magic in Equestria" exam in the school library when they discover a part of the school that no pony else knows about. When they decide to do some exploring, they end up learning much more than they bargained for.
|November 1, 2016||An episode titled "Students Sneak Out" was first planned, listed as #818 in the episode order.|
|November 21, 2016||Episode pushed back to #821.|
|December 7, 2016||Episode pushed back to #824.|
|January 6, 2017||Episode moved up to #822.|
|February 27, 2017||Episode retitled "What Lies Beneath". Premise written by Michael Vogel.|
|March 13, 2017||Outline written.|
|March 21, 2017||Beatsheet written.|
|April 10, 2017||First draft of the script written.|
|April 21, 2017||Second draft of the script written.|
|May 1–5, 2017||Final draft written.|
|May 25, 2017||Script locked polish.|
|July 5–12, 2017||Voice recording in session.|
|October 12, 2017||Animatic submitted for review.|
|March 7, 2018||Client cut of animated episode submitted for review.|
|April 13, 2018||Musical score added.|
|May 22, 2018||Final revisions made to the episode.|
|Yona, Smolder, Gallus, Ocellus, Silverstream and Sandbar|
This episode is only available on Netflix and other digital platforms due to Shout! Factory's 10-year licensing rights having been expired as of 2019.