It's always sunny in Philadelphia Season 9 Episode 7 : The Gang Gets Quarantined
When a severe flu outbreak sweeps through Philadelphia, claiming the life of an elderly neighbor, the gang worries that the rampant bug could adversely affect their voices. With a singing competition – the winner of which will open for Boyz II Men – on the horizon, the gang chooses to voluntarily quarantine themselves inside of Paddy's in an attempt to keep their singing voices pristine. While a solid plan in concept, the execution of their quarantine leaves much to be desired, as no sooner do they begin their self-imposed isolation than they begin breaking all the strict rules they've set for themselves. Meanwhile, Frank, fearing that his age could make him even more susceptible to the flu virus, takes his desire to remain germ-free to a new level of crazy.