When Twilight Sparkle says, "Friendship isn't easy," AppleJack's element of harmony necklace is missing.
When Twilight is reading the friendship reports she sent Celestia and the flashback from "Bridle Gossip" is shown, it is slightly different from the actual episode. Specifically, as the camera is panning out while the ponies laugh, Pinkie stares at the screen until the view fades out; when the same scene is shown when Twilight is reading the report, Pinkie looks at the screen for a shorter time, then looks back at the other ponies.
During the pan shot of the corrupted ponies trying to use the Elements, Pinkie is wearing Fluttershy's necklace.