Nothing new
Sprite movies are really overdone, so it really takes something special/new to even get a "good" rating anymore. This one was really predictable, and where it wasn't predictable it went places everyone else has already gone.
Here's what most Sonic sprite movies do. Just replace "Sonic" with "Knuckles" and, no offense, but that's what you have here:
Sonic is battling Shadow/Metal Sonic/Mario/Etc. Sonic gets his butt kicked, flies offscreen. We hear nothing from Sonic for a few moments, then he reappears in his Super form and proceeds to destroy Shadow/Metal/Mario/Etc. Then something happens that sets up a sequel.
Please, if you're going to make another "episode" to this, do something that hasn't been seen a hundred times over.
Also, I am aware that knuckles does indeed turn pinkish when he becomes super; but the shade you chose isn't right. It's supposed to be pink as in, "light red", not "bright purple". Otherwise it looks too girly.