Derpy, Octavia, and Vynil.
I could actually see it working; "Camp Laslo" did something like that once. It had an episode centered around three background characters. The charactes acknowledge the fact that they always hang out in the background and go unnoticed so they try to make names for themselves (they don't succeed).
I think they could make an episode like the one described above just as one time thing. It could be a little shout out to the brony community.