Hi! I'm not sure how to contact you besides commenting on a post. But as I was re-watching Season 1, during the scene in which Nightmare Moon arrives, the CMC are seen huddled together, which shouldn't have been, considering they don't actually meet until episode 12. Of course, this probably is more foreshadowing than a mistake.
Another thing I'd like to add is the use of background ponies. The same exact audience set is used in Boast Busters, The Show Stoppers, and I don't know what else.