The gif is a little odd, I think it's because during the free fall section, those little arrows behind Sonic and Tails (?) never make it to the top, so it feels incomplete. The sound tag really isn't necessary imo, it ruins the format. The text is fine, though.
Bonus points for the originality and organisation. The gif is a good size and the idea is original enough but something about it really throws me... I think it feels as though the gif doesn't end where it should.
The corrupted image aside. The image is what it is, a screen shot. There's nothing wrong with it. It's not stretched, it's not squeezed. It's fine. As for the subtitle. Stylize it? Maybe like... Italicize it? or make it Bold and maybe change it's color to light green, so it matches the slime theme? You know?