Charlie Kelly is one of the co-owners of Paddy's and is a childhood friend of Mac and Dennis. Charlie is definitely not the smartest of the group and is constantly is financial trouble, lives in a crap apartment, and is stuck doing "Charlie work" (aka janitor stuff). Frank ends up living with Charlie and there's a pretty good shot he's actual his father after a one night stand with Charlie's mother.
I'm going to the crevice!Charlie
No I don't eat dragon, cause, uh, it's not a meal for peasants, it's a meal for kings, and I'm sort of a common man. But they don't eat us, it's a common misconception. They actually eat gold and treasure -- that's why they're always sitting on a pile of it.Charlie