It's Always Sunny in Philadelphia Season 1 Episode 3

Underage Drinking: A National Concern

After reminiscing about high school, the guys conclude that it would be a public service if they allowed teens to drink in the bar, thus providing a safe and controlled environment for teens to party. Feeling that she missed out on a lot as a teenager due to having to wear a brace for her scoliosis, Dee begins dating a high school jock.