Mr. C is a Chihuahua mix, about two years old and will be neutered soon. He's was a bit mouthy when he first came in, but he seems to be calming down nicely. What he really needs is a fenced in yard where he can burn off some of his energy, then he'd settle down nicely inside. He does seem to do well with dogs of his size; we don't know about larger ones.
This goofy guy won't last long - he's too entertaining!