It's Always Sunny in Philadelphia runs on Crosses the Line Twice. Stand-out examples include:
- Charlie eating cereal and watching cartoons in his underwear while wearing the Nazi uniform cap that belonged to Dennis and Dee's grandfather at the end of "The Gang Finds a Dead Guy."
- The ending of "Charlie Goes America All Over Everyone's Ass": Frank's gambling business in the basement has now escalated to a parody of the Russian Roulette scene from The Deer Hunter...and then one of the participants dies as a result of it.
- "Frank Sets Sweet Dee On Fire", in which he does so twice.
- In "Dennis and Dee Get A New Dad," Dennis and Dee discover that a man named Bruce Mathis is their biological father, and take their mother Barbara and Frank to a restaurant to confirm the truth. Ordinarily, such a revelation would be a serious and dramatic scene...but their Barbara's utter indifference to the situation (she treats it as a minor inconvenience at best and has no problem completely upending their lives) and Frank's absolutely brutal Heroic BSoD, culminating in him having a small stroke, make it gut-bustingly funny.
- The "Does This Remind You of Anything?" parts of "The Aluminum Monster Vs. Fatty Magoo".
- The final scene from "Mac Is a Serial Killer" has the gang is trapped in the apartment of a Serial Killer who has been beheading blonde women and storing their heads in his fridge, with said serial killer having just arrived home and has them at his mercy - and then Frank revs up his chainsaw before a Smash to Black, ending with the implication that the gang actually killed someone.
- "Frank's Pretty Woman" doesn't even have a line to cross. From Frank spontaneously marrying a hooker, to Mac injecting shots of insulin mid-chimichanga, Dee pleasuring the actor from "The Gang Gets Invincible", Dennis's anorexia, Charlie projectile-vomiting blood onto a woman in the back of a limo, and everything related to Roxy's death, it achieves a level of vulgarity and inappropriateness seen by few episodes in the series until that point.
- "Frank Reynolds' Little Beauties" from start to finish - the gang spends the episode hosting a Child Pageant, and it goes exactly the way one would expect from this show.
- Frank recounting his experiences at a "nitwit school" in "The Gang Gets Analyzed" is horrifying but also insanely hilarious because of the crude and vulgar way he describes it and because he's reduced to a blubbering wreck.
- The gang digging up Barbara Reynolds' grave in "Charlie's Mom Has Cancer" under the impression that she was secretly alive and that her grave was filled with money? Not unusual for them. Finding out that she really was Dead All Along by finding her skeleton and discovering that Frank had tricked them, causing Dennis to snap out of his inability to feel? Incredibly depraved and absolutely hilarious.
- "The Gang Breaks Dee" has Dee finally get her comedy career off the ground and achieve her life-long dream only to find out that literally everyone involved, from her agents to her fellow comedians to the audience, were actors paid by the Gang to trick her into thinking she'd become a successful comedienne, purely to tear her dream away from her again. It's such a cartoonishly cruel twist that it loops back round from tragic to hilarious.
- What Frank does to cheer himself up, going off "Mac Kills His Dad". He rents a limo and goes around throwing water balloons full of champagne at homeless people, asking them how they like a taste of the good life.
- The Gang having the Paddy's Pub gloryhole double as a Confessional booth so they can trick Psycho Pete into confessing to multiple murders and even cannibalism to Rickety Cricket. He didn't even do it — it was a rumor the Gang spread about him in high school. Cricket then doubles down by saying a confession would be free, but anything else would have a price.
- In "PTSDee", Dee tricks a stripper into shoving his crotch into his estranged daughter's face during a performance as revenge for him calling her his "rock bottom".
- Every instance of Dennis talking about emotionally manipulating women or outright coercing them into having sex with him.
- Mac and Dee donning Blackface to portray African-American characters when the Gang makes their sequels to Lethal Weapon.
- In "Frank Vs. Russia," Dennis roofies his own father, inserts remote-controlled anal beads up his butt, and eventually gets them stuck on the highest setting — which is simultaneously rape, incest, and torture, and certainly among the most depraved things he has ever done. But it still plays as comedy because of the rationale — Frank is trying to use the vibrating beads to help him cheat at a chess tournament — as well as Frank's wildly exaggerated reactions during the game and the sheer amount that the situation escalates.
