She-Ra, perhaps surprisingly for what may be readily dismissed as a "girl's" show, strikes a markedly different theme. Rather than defending the top of the hill, Adora and her team are the last holdout in a world that has already been conquered. Though the effective tones of the series aren't so different, between the comic relief and the "Saturday Morning" restrictions, there's still an underlying distinction which is never so markedly shown* as in the "Secret of the Sword" movie.
In the middle of this quasi-serious tale of a struggle against oppression and hope against hopelessness, the gang take a detour to He-Man's homeland of Eternia, where She-Ra's foe Hordak recruits the aid of local hopeful Skeletor in an assault on their collective enemies. We can only assume that the conversation went something like this:
SKELETOR: Nyah! Yes, I'll help you, but on one condition! Our scheme must involve at least one change of disguise, and this enormous, hollow cake!
HORDAK: What. What cake. What ... I, Hordak, will wear no disguise.
SKELETOR: That's fine! The disguises are for us. You will be inside the cake.
HORDAK: What happened to you, man. Hiding? Trickery? You used to be cool. Where are your armies? We will march on this castle and take it by force!
SKELETOR: Look, after getting beat down by He-Man on a weekly basis for I don't know how long, you start coming at these things sideways. Trust me, we need the cake. Nyah.
So that is what they do. Skeletor and his minions fight their way through the outer defences of Randor's fortress, presumably with this giant cake in tow, wait until they get to the very last door and then disguise themselves as pastry chefs. They wheel the cake through into the dining hall and Hordak jumps out like some hideously misjudged strippergram. And this works, they successfully kidnap their target, and (we assume) waltz on out without any further resistance.
The pair of heroes just got done destroying a laser ray that is fuelled by the tears of the innocent, and now they're dealing with wacky hijinks and oversized confectionery.
I just think it's interesting that the show with the talking flying rainbow unicorn is somehow the darker/grittier one.
* I should note that I am not a scholar of the series, it's possible that halfway through there was an episode where Hordak started putting babies on spikes. I pretty much doubt it. Either way, I'm just making a point.