- Howard's mother. We never see her, she always shouts, and according to Howard, he doesn't live with her, ''she lives with him''.
- Something about Leonard's mother's voice is a bit chilling. She sounds how a female version of AM would. Think of Leonard's childhood. She is really is comparable to the likes of Sofia Lamb and Dahlia Gillespie. The way she Mind Rapes Penny with that smile on her face: that's like Johan Liebert from Monster... forget suicide, it's a wonder Leonard didn't turn into a serial killer! (Sheldon actually once did muse on the possibility that Leonard is actually a violent sociopath, simply biding his time before actually killing him!)
- The worst part is that it's completely Played for Laughs, even when Leonard actually shows how much his mother's behavior upsets him. On top of that, his mother KNOWS that her behavior is abnormal and directly harmful to the development of her children, being an expert psychologist, but she has no interest whatsoever in changing.
- The Morlock scene. A dream within a dream, both with Morlocks that attack Sheldon no matter where he goes with the Time Machine.
- Sheldon's fake smile with his eyes wide open and showing all of his teeth, to the point where it was the page image here for a long time. It's currently the page image for The Unsmile.
"We're here to see Koothrapali, not kill Batman!"
- When Sheldon got even with Leonard for a scare prank. Not the prank itself, but the fact that the audience didn't see that coming.
- Bernadette. Just Bernadette. At one moment, she would be cute, sweet, cuddly, the next moment she would use her scary voice to force you to do things.
- Or let it slip that she accidentally combined Ebola with the common cold, or that she couldn't remember if she washed her hands after working with penicillin-resistant gonorrhea.
- Sheldon's dream at the end of "The Santa Simulation". Sweet moment with Santa: Awww. Santa turns it around and shoots up the apartment with a cannon... Um, yeah, definitely a nightmare. Sheldon's face at the end when he wakes up shows the poor guy is obviously terrified and there's no ending joke to diffuse the tension for the emotionally confused audience. The audience that just saw Santa. Try. To. Kill. Sheldon.
- The episode when Howard eats peanuts in order to keep Leonard away from his apartment for a surprise party. Howard's swollen face was TERRIFYING.
- Sheldon gets 25 cats replace Amy in his life. The episode is hilarious and cute but this line is jarringly disturbing.
Leonard: Fine then, live with cats, be like my aunt Nancy! She had dozens of them and you know what happened after she died? They ate her!
- Sheldon's response to the Rorschach ink blot test:
- A: A bat.
- B: A bat.
- C: A bat.
- D: My father killing my mother with a hypodermic needle.
- In the episode where the guys fight over a prop of the One Ring, Sheldon has a nightmare where he gets it and becomes Gollum. It isn't a pretty sight, and is currently the page image. Sweet dreams.
- Literally, and in-show: for Penny (and Leonard), it's Howard and Leonard's explanation of how Sheldon might reproduce.
Howard: I'm an advocate of mitosis. One day he'll eat an enormous amount of Thai food and split into two Sheldons.
Leonard: On the other hand, I believe he's the larvae form of his species and one day he'll split the cocoon and emerge with moth wings and an exoskeleton.
Penny: Okay, well, thanks for the nightmares.
- In Season 5's "The Infestation Hypothesis", it's never shown what exactly was crawling around inside the chair Penny picked up off the street. Its size, shape, and movements seem to indicate a mouse or a small rat, which would be scary enough, but the fact is we never find out for sure.
- Earlier in that episode, Sheldon has a horrifying Nightmare Sequence involving a swarm of roaches crawling out of the chair and burying him alive.
- It was already pretty friggin scary but after Bernadette lets it slip that she and some other microbiologists crossed Ebola with the common cold Leonard asks, "Why would you do that?" and Bernadette responds "We didn't. That would be a terrible, terrible thing." all the while wearing a huge smile on her face. Brrr.
- When Howard digs out his childhood set of magic tricks from the closet, he discovers the "dove in the pan" trick still contains the dove.
- Raj trapped in Mrs. Wolowitz's house.
- When telling stories about what life would be like if they never met Sheldon, Howard's story involves his mother being dead and it's unknown if she died naturally or Howard killed her. He still has her body and treats it as if she is still alive.
- The face. Oh god, the face. Also the fact that this is still the closest we've come to seeing Howard's mother properly.
- Not to mention Howard's creepy expression as he finishes telling this story. He's not just imagining, he's fantasizing.
- Bernadette's fake laugh is one of the most terrifying moments in the series so far.
- Early in the first season, Penny lets slip to Sheldon that Leonard may have made light of Sheldon's accomplishments. The sight of a genuinely pissed-off Sheldon, towering over Penny as she backs away, demanding to know what exactly Leonard said. Up to that point, Sheldon had largely been played as a Cloud Cuckoo Lander, but seeing that scene, you could very easily believe it when Leonard says that Sheldon is one lab accident away from becoming a super-villain.
- When Howard is going into space the gang is sitting in the apartment watching the launch together. It's a heartwarming scene. It becomes Nightmare Fuel when you think about the Challenger disaster and consider what if it was your own friend/spouse in Howard's place.
- Stuart's entire life. His misfortunes may seem funny to us who watch him, but try to put yourself in his shoes. His life is basically an endless series of nightmares that come true.
- The two HUGE rats that attack Raj in "The Expedition Approximation."
- In "The Hot Troll Deviation", Howard, using a recording of Sheldon saying "Penny", tricks Penny into opening the door by imitating Sheldon's signature knock. Penny then states she wouldn't have opened the door if she knew it was him after he gave her a teddy bear that turned out to contain a webcam.
- Leonard's red and raw body when he removes the sweater in "The Itchy Brain Simulation". And then to find out that Sheldon deliberately manipulated Leonard into wearing it for days. "One lab accident away" indeed...
- Bernadette threatening an airport employee to have her mother in law's ashes found and returned to them with murder (albeit used for comedy), one only has to wonder why she didn't call security on Bernie. But imagine trying to do your job and it's really stressful and demanding and then comes the situation of lost luggage and having to locate it. Now, you can always expect your customers to be upset and extremely angry with you but one of them threatening to kill you if you don't do your job?
- Raj and Howard are watching horror films in order to prep Raj for his date with Emily. The two are completely freaked out by the movies she picked out. Howard verbally sums up what they've seen so far, and it's stuff far more horrific than you're ever likely to see in any mainstream horror film. Raj isn't sure he wants to date someone who watches that kind of film, and he questions Emily about it. Her response? "They kind of turn me on." Raj is too horny to consider the implications and just presses play, but just think of what that means, what kind of terrifying things must go on in Emily's brain...
- Far more horrific? Goodness, no. The movie they discuss watching is 100% real. Sweet dreams.
- In one episode, Leonard comments that nobody goes into science for the money, at which point Bernadette dismisses him with a "Speak for yourself, my research team just invented and cured restless eye syndrome. Kaching ya blinky chumps!" The idea of scientists inventing new diseases just to make money off the cure is deeply unsettling in how sociopathic it is.