A sonic Chao is a kind of Chao, that as you would expect, looks like sonic.
How to make (Part 1) Edit
To make a basic Sonic Chao, get a normal Chao, and give it more run animals and drives than other stats. Once it evolves, it will be green, with spikes on its head. Now you have the choice of basic or advanced.
Basic Sonic Chao Edit
To make it a basic Sonic Chao, just have the Chao's second evolution be normal, you can do this by either not giving it more stats, or making sure all its other stats are equal. Once its a Basic Sonic Chao, its spikes will be longer, it will be a lightish blue, its ears will be more like sonic's, and it will have dark green coloring on some areas.
Advanced Sonic Chao Edit
To make it an Advanced Sonic Chao, keep giving the Chao run stats more than others after evolution, it's spikes will curl down, it will turn a vibrant blue, its ears will get bigger, and it will have black coloring on some areas.