That's right, on November 20, 2008, FXX's It's Always Sunny in Philadelphia S04E13 "The Nightman Cometh" would begin setting up its permanent home in our brains for the next 14 years.

‘The Nightman’ song evolves into ‘The Nightman Cometh’ musical In the final episode of It’s Always Sunny in Philadelphia Season 4, ‘The Nightman’ song effortlessly transforms into ...

That's when S04E13 "The Nightman Cometh" first aired, a musical masterpiece that's as enjoyable on its 86th viewing as it was on its initial viewing (or so we're told… don't judge us).