Dennis is a five-star man, and don't you forget it. As a friend, Dennis is terrifying. He views his friendships as transactions. He keeps detailed mental (and physical) dossiers on everyone’s weaknesses.
Charlie is the wild card. Illiterate, addicted to glue, and king of the rats, Charlie is the heart of the group precisely because he has no heart. He is pure id.
Most friendship advice columns tell you to set "boundaries." The Sunny gang has anti-boundaries. They pick locks. They read diaries. They install hidden cameras in the bathroom.
While there is no specific episode of It's Always Sunny in Philadelphia titled "