"You have the option to collect chao, a special creature that will grant your characters various bonuses. Unlike previous titles (even Pokemon) there is no way to breed/raise them. Their abilities can become more effective as you use them and level, but once I acquired a few over-powered chao early on I never felt a difference. I also never saw a need to change them after I found a set that worked for me.
All of that aside, this is the first Sonic game in a long time that I've felt compelled to play to completion."