So remember the episode, Amending Fences? So during the events of the first episode of the series, Twilight Sparkle friends (old ones) were telling twilight sparkle that Moondancer was having a party.

In the said episode (Amending Fences), Twilight Sparkle and Spike reunion with her old friends (forgot their names will add them later) and since throughout the entire series timeline (offscreen to be exact) Moondancer has never been her self… anyways during the flashbacks when they both were fillies they both had similar mane styles and in the video talks about why it's like that.