Carl is almost always seen with his friend and co-worker, Red. They first appear in Saturday, Bloody Saturday when Kevin catches them stealing cigarettes from a vending machine at the airport. The two quickly befriend Kevin. He is a high school drop out who enjoys drinking and doing drugs. He and Red regularly steal from the suitcases of passengers, looking to score prescription medication they can take recreationally.
Carl came up for an idea for a movie entitled "Fuck School", in which "people still go to school, but they fuck." He and Red are now in developmental stages of the film.
He is not only uneducated and dimwitted, but he is incredibly selfish and seems to have little regard for human life, as demonstrated when he laughs at the video of his former boss's death, and by stealing medication from passengers.
Carl and Red endanger and act irresponsibly towards their boss's 14 year old son. They provide him with alcohol and cigarettes, allow him to take an unknown prescription pill (and to mix it with alcohol, increasing the potential risk), and encourage him to quit school. Later, they show him the graphic security footage of Ed being decapitated by an airplane propeller, which horrifies Kevin.