Now this really is an original idea. Aging characters is nothing new, but doing it with animal characters is brilliant! I admit that I don't know what the teenage thing means. It's probably just some generic term for them. I mean, they're mutants, so they probably wouldn't age. I recognize the red color.
Yeah, it's great that you add depth to something many people consider silly. Then again, the original comic books were more serious. Seriously, they were! At least he's of legal drinking and smoking age. Middle aged ones would be bad too.