I don't know what point there is in really giving this one an in-depth review since it's a self-described shitpost, but I'm already committed to the bit so let's just run it.
Spoilers from here on, for all that matters here.
Implementation of Theme:
Not really present, and I don't think anyone cares. I mean, I guess there's some "darkness" in Free dealing with his gravitational mixup and some "light" in that being resolved, but it's pretty thin.
Story:
Also not really present, if we're honest. There is a premise here that's used for a few quick jokes and then we're done. Ultimately, I just don't think the humor really lined up with mine, though a few jokes like the absurdity of the wolf turning into a car and the commemorative badges for seeing Free did get me. Honestly, I don't know much about Sonic lore either but the random fanfic at the end kinda felt like the best part, to be honest.
Presentation:
Actually kinda solid. The upside-down sprites were fun, there weren't many typos or other language errors, and the music weirdly just kinda slapped? Like I was just jamming the entire time.
Creativity:
The whole upside-down thing is really kind of a neat idea. I think if you had taken more time to flesh it out, you could have actually had a really solid parody, which would have been really welcome amidst all the drama of many of the other entries. As it stands, it's good for a quick chuckle or two and I don't think anyone can really complain about that.
I rate this 18 bottles of gravity juice out of 3 chaos diamonds.