While Twilight is meeting the Apple Family, she gets a green apple shoved in her mouth before Granny Smith was introduced. When Twilight spits the apple out later on, it is red.
Apple Bloom, Sweetie Belle and Scootaloo were seen in one shot huddling under a table in fear of Nightmare Moon even though they didn't meet each other until 11 episodes later in Call of the Cutie.
While Fluttershy is walking with Twilight, Twilight's eyes turn black for a few frames.
Before Pinkie's really long gasp after Twilight says hello, her upper eyelashes are upside down.
While Twilight is bashfully saying hi to Pinkie, her bangs have two splits, when it should have one split opposite her hair stripes.
While Twilight is walking with Pinkie in the library, the sounds of Pinkie's hooves are heard, but not Twilight's.