Charlie is overheard repeating a racially charged comment by the Waitress, leading him and Mac to desperately try to prove they aren't racist by seeking out black friends.

Terrell’s promotion is so successful it turns Paddy’s into the city’s hottest gay bar. While Charlie and Dennis initially embrace the huge profits and attention, Mac and Dee hatch a scheme to return the bar to "normal". Key Themes & Impact

The Gang Gets Racist | It's Always Sunny in Philadelphia Wiki

Dee introduces her friend Terrell from acting class to help promote the bar.