I just re-watched Castle Mane-ia on a whim. I haven’t really re-watched a lot of season 4 yet, or any ponies at all in quite a while, so it sounded like a fun thing to do. I had a lot more fun with it this time! I mean it’s basically the mane six all running around being cute and silly while Twilight geeks out over old books. A couple thoughts:
I’d forgotten that this is the episode where they start the diary. And I really liked, as a bit of foreshadowing, how Twilight said they could write down the lessons they learned and maybe other ponies would read them and learn from them someday. Just since the whole thematic arc of the season is about how by choosing to do the right thing they inspire other ponies to do the same. I thought that was really cool.
I’d also forgotten that at the end, after everypony’s had a laugh about how silly they were all being, there’s actually an evil shadow with glowing eyes lurking in the background. And like, I dunno if it’s really meant to be anything more than a cool surprise. But I figure that’s gotta be Tirek, huh? I can’t think of who else it’d be.