In the episode “Roll With It” in season two, the cast dons their classic costumes for a playful episode in which characters’ plans are acted out in dramatically different tones and art styles. This doesn’t so much add to the canon as show the creators having fun with the franchise’s various iterations. It does introduce another reference that paid off later: Catra’s original series ability to transform into a feline “beast.”
The Honor of Grayskull
“For the honor of Grayskull!” has been part of She-Ra and the Princesses of Power from the beginning, with no one really commenting on what a very specific phrase it is that seemingly has nothing to the characters. In season five, Adora finally finds a reference to it, with the help of Bow’s dads. Grayskull was a rebel group, which a former She-Ra named Mara worked with in order to overthrow the people trying to harness Etheria’s magic. Season five has a rough environmentalist message, with the First Ones revealed not as all-powerful sages but people grabbing for resources. But magic is a resource Etheria would have in abundance, if only the First Ones’ tendency toward tech and weapons hadn’t gotten in the way. Mara sacrificed herself to make sure their greatest weapon couldn’t fire, and now, with the introduction of the Grayskull group, we know she didn’t work alone.
Their existence complicates the space operatics of the First Ones even further. We now know there were three groups involved: the First Ones who settled Etheria and created the network of magic-users (including She-Ra) as a weapon of mass destruction, the rebels, and the evil Horde.
In the toy line and shows that formed the previous He-Man franchise, Grayskull was a castle that held powerful magical secrets. Different iterations of the story added more or less detail to this, with the 2002 reboot adding a King Grayskull who was the first to use He-Man’s magic sword (the tagline / transformation spell “By the power of Grayskull!” therefore referred to him).
Mara’s rebels turn Grayskull from a spell into a military designation. The Star Wars-style story of a rebellion pushes She-Ra a little further toward the science fiction side of the science-fantasy spectrum, as Mara’s story had before. For example, Mara’s friend Light Hope, formerly a magical spirit, is rebooted as an artificial intelligence.