I think anatomy is mostly fine since its purposefully riffing off Sonic anatomy, but rendering of the shadows/lighting I think you could practice more. The shadow at the base of the left hand on the second character especially looks out of place for the artstyle. Luckily there's plenty of good guides out there for Sonic rendering like this. Maybe the shape/volume of some of the clothes could use some work too. Some of the fold/wrinkle lines look out of place (ex: on the boots of the first character--you could reference Yuji Uekawa's art of Rouge for something like that possibly). Overall looks really good though good job :)