Many of Dennis's sketchiest moments happen in later seasons, as his psychotic behavior gets darker. By the end of Season 12, he's a full-on maniac who refers to himself as a "Golden God" and carries some concerning equipment in his trunk.
Here are some of the creepiest Dennis moments in It's Always Sunny in Philadelphia history.
Dennis's desire to use the "implication" of danger on a boat plays out in a disturbing way in the Season 11 finale when he meets an attractive young woman on a cruise ship. After following her around the ship, Dennis terrifies the young woman by admitting that he's been following her "in a good way" and explaining that he can do magic - revealing her ID that he took earlier.
The terrified girl grows more nervous when lightning strikes and Dennis propositions her.
"I suspect that, maybe, you might say no. And yet, I also feel like maybe you wouldn't dare," Dennis threateningly says before the petrified young woman runs away.
"Well that's not supposed to happen," Dennis says to himself.
When Dennis, Charlie, and Mac buy a boat in order to impress women, they end up having to do a lot of work on it to get it in good enough shape. Dennis and Mac go out to buy supplies, where Dennis tells Mac that he needs to buy a mattress.
Mac questions why they'd need a mattress and Dennis explains that it would be for taking drunk women below deck where they "can't refuse" him because of "the implication."
He then proceeds to explain to an uncomfortable and concerned Mac that he's simply trying to create an implication of danger for women so that they sleep with him, but swears he'd never actually hurt them.
It's arguably the creepiest moment in Sunny history, and that's saying a lot.
In a moment that is a series favorite for Sunny fans, Dennis berates Dee in a doctor's office after she speaks in accents and makes up stories in front of the doctor. He quickly loses his cool, unleashing a terrifying threat on his sister that leaves her speechless.
"Dee, I swear you would be of more use to me if I skinned you and turned your skin into a lampshade. Or fashioned you into a piece of high-end luggage. I could even add you to my collection!" Dennis proclaims.
"Are you saying that you have a collection of skin luggage?" a terrified Dee asks in response.
"Of course I'm not, Dee," he responds. "Don't be ridiculous. Think of the smell."
At the end of Season 7, the gang goes to their high school reunion and relives the awful days of their teen years. Dennis, in particular, has a rough night after propositioning his former friend's wife as a means of revenge. When she refuses, he loses his mind and barrels out to his car to retrieve a few things.
"What the hell are you doing?" Frank asks.
"She rejected me. Me, Frank! Me. The coolest guy in the history of this godd*mn school," he says. "Oh, they're all gonna pay. They're all gonna pay the ultimate price."
When asked what he has in his hands, Dennis explains that he has "tools" that include duct tape, zip ties, and gloves.
"Why do you have a bunch of weird tools in a hidden compartment in your car?" Charlie asks.
"Fetish sh*t," Dennis responds. "I like to bind. I like to be bound!"
In the Season 8 episode "Frank's Back In Business," Dennis assumes the identity of a man who leaves his wallet at Paddy's Pub and ends up with box seats at a baseball game with two entrepreneurs. It turns out that Brian Lefevre, the man Dennis "becomes," is a controlling shareholder of a company and was being wooed at the time.
During the meeting, Dennis explains to Mac and Dee that he has a particularly disturbing motive for becoming Lefevre.
"This is about much more than just business," he says. "This is about the thrill of wearing another man's skin. Feeling his innermost wants and desires, and being in control of his every single move. That's how you get off. Now, don't you guys wanna get off with me?"
At the end of the episode, Dennis finally "gets off" when his true identity is uncovered at a shareholder meeting.
In the Season 5 episode "The D.E.N.N.I.S. System," Dennis reveals his comprehensive (and creepy) system for seducing women. Each letter of his name represents another step of the system:
D - Demonstrate value
E- Engage physically
N - Nurture dependence
N -Neglect emotionally
I - Inspire hope
S - Separate entirely
It's one of the most twisted ideas in Dennis Reynolds's almost 15-year history on the series and a system that doesn't seem to ever work out for him.