This has been floating around for a while now, but for those that missed it, Tara Strong and a bunch of other big names in voice acting recently jumped on a Star Wars radio play at Emerald City Comic Con. It's not completely pony related, but Twilight Sparkle does make an appearance at 58:40 to 1:02:00.
They also tossed another video up pretty recently! Check out both after the break!