Nightmare Fuel: It's Always Sunny in Philadelphia

  • Dennis and Dee's vacation to the Jersey Shore gets really dark really fast when they tag along with a gang of criminals led by a dangerous, trigger-happy dusthead who gets one of his partners shot in a botched robbery, murders a doctor right in front of them, and is in the middle of making them dig their own graves when they finally make a break for it. All of this is scored by The Go-Go's "Vacation".
    • In the same episode Frank and Mac ended up lost at sea with their liferaft on the verge of sinking. Sure, they were saved when the party boat filled with Jersey Shore-style guidos happened to pass by, but that whole scene was a definite Paranoia Fuel. The only member of the crew that came out with nothing really bad happening was Charlie, save for the fact that the Waitress being nice to Charlie was the result of her being high on ecstacy.
  • Charlie tells Mac that he shouldn't get all worked up about his parents stealing other people's gifts, posing it as a holiday tradition. Then he says to Mac that he handled the news about his mom whoring herself out to a bunch of "Santas" on Xmas day quite well and then procedes to bite the Mall Santa's neck, asking him if he fucked his mom. Despite being a funny scene; it's still kind of scary (and sad) to see a guy biting a mall Santa's neck so hard that he bleeds and repeatedly yelling "Did you fuck my mom?" and "Did you fuck her?" without any evidence to support that he ever did, especially since the acting is very believable. Poor, unfortunate mall Santa.
  • What the gang subjects the "Juarez" family to in the Extreme Makeover episode.
  • Frank's Sanity Slippage over sanitizing everything in "The Gang Gets Quarantined".
  • Psycho Pete, Mac and Charlie's old friend and gang leader, killed and ate his own parents.
    • He gets set free due to his institute shutting down in "Psycho Pete Returns" and it turns out that the parent-eating thing was a rumour, and in reality Pete had been institutionalized for depression and social anxiety. The fact that it may have been partially fueled by the gang spreading rumours about him is Nightmare Fuel in itself, though.
  • "Charlie's Mom Has Cancer" ends on a pretty gruesome note. Dee has been led to believe that her mother, Barbara, is still alive, and has stashed a large amount of money in her grave. In the end, the gang digs up said grave, only to find her decomposed corpse. Everyone reacts with revulsion, and Dennis is especially traumatized. The worst part is that Frank set this whole thing up, as revenge for Dee saying that his mind is slipping. Rule of Funny redeems this somewhat, but it's at least as horrifying as it is funny.
  • An overlooked bit but still very nightmarish in a sense. Most sitcoms go on an episode by episode format, meaning after thirty minutes, the problem is solved and the day is saved for the most part, but the downside is that there is no continuity. Sunny is all in the same continuity, even if there is an adventure every episode, meaning any and all amoral choices the Gang makes has last longing effects on their characters and their world. Need an example? Look at poor Rickety Cricket.
  • To those suffering from depression or those who know someone that suffers from depression, Dee going through it in "The Gang Broke Dee" can be a little unsettling, especially with all the suicide references.
  • When Dee wanders into the hallway of Charlie's building in the middle of the night in "Dennis Reynolds: An Erotic Life". It's a creepy hellhole, and ends with a reference to The Shining. Turns out Dee got high on glue.