Everywhere seems to have produced a pair of Sonic slippers, regardless of the result. These from the Australia SegaWorld, have 3D sewn-on plush heads. The likeness is very 'cartooney' with big attached eyes and a 'front style' mouth that is not quite characteristic of him. The result here though, is at least semi-cute unlike a few other slipper-disasters which can be found about the site.
Here's a photo of the colorful Sonic face slippers. The faces have the distinctly 'cutesy' look for Sonic with the large, close mono-eye & oval nose that is easy to recognize. The back of the head has sort of rudimentary spikes as it's attached to the toe of the slipper. They are also typically colorful with yellow interiors and red tops to go with the blue of the plush heads. These MAY be a different view of the above pair.
Photo discovered by Sonikkou-No-Uta