Heartwarming / Princess Celestia: The Changeling Queen

• Blueblood knew all along that Celestia was a Changeling. She's still his beloved aunt.
• Alternia comforting Luna after the latter realizes how much trouble's she's caused through beating Celestia to within an inch of her life as Nightmare Moon as well as all the trouble she's caused Alternia as a result of it; she can't understand why Alternia doesn't hate her. Alternia admits she did at first, but a thousands years of perspective culminating with Luna's return meant that Alternia had come to see Luna not as a symbol of all that Alternia hated about Celestia or as a pawn for revenge, but as a new sister she had been missing the previous millenium.
• Cadence making up with Alternia in chapter 17.
  Cadence: Mother, would you give me away?
• Chrysalis and Lamia reconnecting with Cyndra, Chrysalis ultimately choosing her kin over the law of the hive and her own anger over Cyndra's betrayal.
• Cadence's impassioned plea for Equestria to accept Alternia when "Celestia" is exposed, because "we are her hive."