Prior to his It’s Always Sunny in Philadelphia guest appearance episode, Dee (Kaitlin Olson) and Artemis mentioned that they are huge Josh Groban fans, Grobanites one might say.
In It’s Always Sunny in Philadelphia Season 9, Episode 6, “The Gang Saves the Day,” the gang hides out during a convenience store robbery.
In his brief cameo, Josh Groban sings a song that references the many insults that Dee hears frequently from the gang.
They marry, but unfortunately, she divorces Josh Groban to marry Brad Pitt.