Originally Posted by Brian278
Once, from Deadspin. It's also featured in the It's Always Sunny in Philadelphia episode (I believe before the Rickrolling phenomenon) where the song is featured during the montage in which Charlie takes a waitress shopping after Dennis and Dee give her money to have sex with him when he tells Dennis he has cancer, ironically in an attempt to cultivate sympathy from said waitress after he sees her wearing a "Livestrong" bracelet. That first season was fucking genius.
Dennis is also caught listening to Rick while driving in another episode. It's a regular Rickfest.