Takes place after the events of Sonic SATAM.
During MLP:FIM season 3

Now with Robotnik gone, all that's left is to fix the problems he left behind, the main issue being his robot slaves. When finding a description about a lost civilization within the computer Nicole, Sonic searches for what's left of the empire known as, Equestria, in hope of finding anything that might help with his problem. Things would go a lot more smoother if Naugus didn't interfere.

The ponies are anthro (just like Sonic).
And Sonic's personality will be that of the SATAM series.