Charlie often screams to get his point across and refers to the dirty work of the bar as "Charlie work".
Charlie is the janitor at the pub, and a known illiterate.
Charlie is also an alcoholic and chronic inhalants user who suffers from various psychological problems including but not limited to anger management issues and possible borderline personality disorder.
Brad Fisher (Nick Wechsler) is first introduced as the Waitress' fiance in the season 5 episode "The Waitress Is Getting Married".
Brad dated both Dee and the Waitress in High School but both dumped him because of his acne.
It is heavily implied throughout the series that Mac is gay, even momentarily coming out of the closet in season 11, and again in season 12, although this time permanently. Dennis is Deandra's twin brother and co-owner of Paddy's. Some episodes hint that Dennis may be a serial killer and rapist, though this remains ambiguous, with one episode suggesting that he collects suitcases made of human skin.
He also displays anti-semitic views, driven by his Catholic upbringing. He is narcissistic, selfish, histrionic and vain, perpetuated by his Ivy League education at the University of Pennsylvania. He even threatens to kill his sister, cut her body into small pieces, and put those pieces into a glass box and put it on display.
He constantly carries a gun with him and frequently pulls it out for any number of situations.
He used to be a successful businessman with a long history of illegal operations (such as running sweat shops and drug-dealing) and dealings with sordid characters.
He doesn't believe in or trust psychiatrists, and was admitted into a school for clinically insane children for a short while as a child, before he was cleared of any legal mental issues and received a certificate stating that he did not have donkey brains.
He is frequently seen in strip clubs, and sleeping with prostitutes (even becoming engaged to a "crack whore" in the season 7 premiere). Artemis Dubois (Artemis Pebdani) is one of the more frequently recurring secondary characters, introduced in "Charlie Gets Cancer" as Dee's friend from her acting classes who acts out a scene from Coyote Ugly (a film that featured Kaitlin Olson in a small part).
Brad returns in the season 7 episode "The High School Reunion" where his face is scarred from the hornet stings.