I didn't really understand this one. How was it that Applebloom didn't already know about Sweetie Belle and Scootaloo? They all seem to have only one teacher, Cheerilee.
That's a major Plothole, i could understand Scootaloo just appearing there, but Sweetie Belle is Rarity's sister. Is it possible that she did not exist until this episode?
But Sweetie Belle not being a part of the story until this point is a plothole. I say if she's Rarity's sister, she'd appear earlier in the show. ...IF she's Rarity's sister.
It's a cartoon no normal person looks that deeply into it! But yes they probably hadn't planned to include her before hand although I doubt they made her up as wasn't she on G1-3 or some other MLP?
Hmm. Now you mention it yeah she might very well have been, I'll need to check that. Celebration 'ewok' scene at end of ep2 maybe?
Oh yeah... Still doesn't explain why she hadn't returned back into the series and why we didn't see her or know her as Rarity's sister. I was kind of "Shocked" when i learned that she was Rarity's sis, i was like "Rarity has a sister now?"
As Faust stated, Sweetie Belle doesn't live with Rarity. She only visits her. And yes, they probably didn't notice each other, and Diamond Tiara probably bullied them (as they appeared and hid from her like Applebloom did).
I read somewhere that in the first episode, you could see the Cutie Mark Crusaders talking. I haven't noticed it, maybe you can try and see if they're there.