It's Always Sunny In Philadelphia: 10 Most Disturbing Episodes
5. Mac Is A Serial Killer (Season 3, Episode 10)
The Gang investigate a serial killer stalking and slaying attractive blonde women around Philadelphia. Frank and Charlie suspect a secretive Mac, who is hiding his new relationship with a trans woman. Dennis and Dee don’t believe their friend is smart enough to be a serial killer.
The Reynolds siblings decide they need to walk in the killer’s shoes, choosing the Waitress as their victim. They get their “killing tools” for free as Gary, a hardware store employee, is in love with Dee.
Dennis, as a house painter-cum-serial killer, and Dee, a psycho clown, discuss how Dennis will strangle the Waitress and Dee will chop her up into pieces. Dennis’ sexual excitement needs to be tempered by reality. Stumped by Dee’s squeaky clown shoes and the Waitress’ pepper spray, Dee and Dennis jump on the investigation into Mac.
Dee uses Gary’s flat for the Gang to lure Mac into a To Catch a Predator-style sting. Before Frank can get a confession via chainsaw, Mac reveals his secret. Charlie opens the fridge for a beer, only to find “15 or so” severed heads. Easily the grizzliest visual in the show’s history.