After watching A Diamond Tiara and Sweetie Belle This Day Aria, I thought:

What if Queen Chrysalis captured the real Diamond Tiara when she was a baby, and Diamond Tiara is actually nice, and doesn't have her cutie mark?! Maybe Chrysalis took over her body!

After watching "Friendship Is Witchcraft|6| Lunar Slander" I thought:

What if that's the real reason ponies are afraid of Luna? After all, she was sent to the moon for 1,000 years and doesn't fit too well into modern life.

After Watching S04 EP25: "Twilight's Kingdom" I thought:

What if real rainbows really represent the magic of Friendship?

After Watching "Friendship is Witchcraft|9| Seed No Evil" I thought:

What if that really WAS the ending of Snowdrop? Where she sees? And THEN the other things happen?

These are just my random thoughts. Feel free to post some more that you have in the comments.!