C2 looks like Carl, sounds like Carl (with a higher-pitched voice), and walks like Carl. As an identical clone of Carl, he passes as Carl. Whenever Carl doesn’t want to do something, C2 is the one who is there to substitute. He's much sweeter and more naive than his DNA donor, however, and also much more motivated. He enjoys being at Carl’s service, and fails to see that Carl allows him to go to school, not as a favor, but to prevent himself from having to exert any kind of effort.
Not only does he have 95% of Carl’s DNA but also 5% of him is from Rex (because the dog apparently contaminated the sample), which is probably why he enjoys catching Frisbees in his mouth and eating dog treats. C2 has two webbed toes together, unlike Carl.
C2 wears the same clothing as Carl throughout the show.