Here's a link to a flash game i found where you stop changelings from invading http://futzi01.deviantart.com/art/Canterlot-Defender-303305344 (http://futzi01.deviantart.com/art/Canterlot-Defender-303305344)
enjoy :D
(up, up, down, down, left, right, left, b,a, Enter) ;)
Played this before, and I'll say what I've said about it before (not on this forum).
-Rainbow Dash is worst assist.
-Fluttershy is best assist.