Sonic / Knuckles / Tails sprites hidden on each track.
Each track has multiple hidden Sonic/Knuckles/Tails sprites that are usually only found by going in reverse. Shoutout to Boundary Break for finding one of them and sending me on this chase.
Tails, side of barricade before start line.
Sonic, rock wall next to "stairs" in front of start line.
Sonic, rock wall in front of start line.
Sonic, bottom of pillar next to loop.
Knuckles, top of pillar.
Sonic, behind arrow sign.
Sonic, on the ice wall next to these tires near the end of the lap.
Knuckles, on the back of this red machinery before the shipping crate section.
Sonic, hanging off the back of this smoke shaft, after the open lava part.
Knuckles, on the side of... this thing.
Sonic, on this stack of yellow poker chips before the end of the lap.
Sonic, on top of this purple roof.
Knuckles, behind this rock on the first big turn.
Sonic, on this last jump before the warp room.
Knuckles, on this wall near the start line.
Sonic, on this wood post.
Knuckles, on this exhaust pipe.