- From Big Brother 2: Justin Sebik's legitimately psychotic behavior and drunken madness, infamously warranting the first-ever contestant expulsion and the permanent removal of unrestricted access to alcohol on the US run. As the game went on, something about him rang out as... off. It started with urinating on a window and smashing up a chess set. Yet later, he became an actual threat to contestants' well-being, threatened them with violence, and brought a knife up to Krista's throat. It was such a severe incident that he was immediately ejected from the game, and the incident preceded what was supposed to be a live episode and Julie remarked it is one of the most serious offenses someone could commit on the show. What he did was so serious, the producers cut away from the footage and had Julie explain what happened by word of mouth. Even scarier, Krista was too drunk to reason and inadvertently tempted Justin to keep bringing the knife up to her neck. It was seriously fucked up, even by this show's standards. Because of what he did, Sebik is now the most hated contestant on record. And this was only two seasons into the US run of the show!!Julie: At this point, Justin picked up a large kitchen knife and repeated to an intoxicated Krista, "Seriously, would you get mad if I killed you?" He put the knife to Krista's throat as they kissed. He then took the knife away momentarily. With Krista's encouragement, he put the knife back to her neck. They kissed again, and then he returned the knife to its drawer.(cut back to footage with them in the kitchen)Julie, voice-over: At this point, Justin was called into the Diary Room.Supervisor: Justin. Please go to the Diary Room.Justin: Ah, boy. We got problems... I think it might have been that knife to your neck...(cut back to Julie)Julie: After a lengthy consultation with the show's psychologist, producers were left with no choice but to expel Justin to protect the safety of the houseguests.
- Worse, the incident occurred late at night and witnessed by nobody but the camera watchers on high, when most guests were either in bed or elsewhere- in a normal setting, this could have been disastrous. Justin was quietly dismissed from the game without any fuss raised until next morning, when houseguests learned straight from the horse's mouth that Justin had suffered the punishment of expulsion, and not only did it deeply hurt some of them (while others joked about it and even mocked the fact he has a boat operator's license lying around), it was compared to as though he had just died and didn't get to pack up or say goodbye or anything.
- Worse yet, in the post-expulsion interview he has with Julie, Justin denies that what he said is disturbing and even calls anyone who thinks it was a threat an idiot and that he doesn't know what kind of glasses they're looking through. Julie has to remind him that there are people on the outside watching the show and might interpret what he said differently or be frightened of his dangerously off-kilter remarks. Justin doesn't even understand why he got thrown out of the house and thinks he deserves to go back inside.
- Scariest of all, that moment was captured right on the live feeds for us to see for all time. They didn't have the chance to cut away like the show did. Genuine proof that he couldn't come back into the house.
- Similar to Justin, but in many ways so much worse, is the severely deranged behavior of Scott Weintraub, coincidentally also a bartender, in Big Brother 4. Scott's sanity wanes after being forced to live under the same room as his ex-fiance Amanda Craig, culminating in him trying to get himself thrown out of the game by throwing chairs and threatening to hit people with oversized chess pieces. Scott starts smoking like a chimney and becoming increasingly hostile towards everyone and ranting about how the game is treating him like a puppet, before finally wrecking the meeting room and ignoring an emergency call to the Diary Room to prevent him from continuing to go berserk. He then calls the whole house in for a group intervention, where he announces his decision to forfeit the game. It's also made evident that when he did finally go to the Diary Room, he was declared unfit to participate any further like Justin. Some people even speculate that he has syphilis, which is causing mental issues for him. And because of this incident, Amanda was the next to go.
- It also doesn't help that Scott's ex-fiancee later had sex with someone else in the house and it was shown on TV. Scott almost certainly found out about that, on top of being unable to move on from his ex-lover.
- The creepy mime in Big Brother 4, especially when he put on a mask and tried an Exorcist crawl.
- The tense backyard showdown in Big Brother 6 between Kaysar, Ivette, and Eric. The latter two are angry Kaysar has apparently been making personal attacks on their character and personal lives, and Eric has been very clear from day one to all of the house that one thing he will not tolerate is any attack on his family. Worse, another conflict has bothered the house beforehand: Michael has been going around making advances when they weren't wanted and Eric intervened on behalf of the house to stop him from causing any further discomfort to the women. Michael took this personally because he feels like he's beeing treated like a pervert, and walks out into the backyard as one fight is starting to brew and both Ivette and Eric are about a hair's breadth from losing their tempers on Kaysar. Then, Michael starts to shoot some nasty sideye at Eric from by the hot tub. Eric glances over a few times and notices Michael, and then Michael leers at him agressively and Eric takes it as a challenge. Michael eggs him on and Eric seems to think Michael also wants to go after his family and then leaps up from his chair so fast he knocks it over, immediately bearing down to get into what may very well have been a physical altercation, had all the other houseguests, even Howie, not stepped in to hold the two back. Production intervenes and forces Michael to go to the bedroom, and Eric to the Diary Room. But that isn't the end of it. Kaysar and Ivette continue to argue after this fight is broken up and then Kaysar angrily springs from his chair and bears down on Ivette, causing another crackdown where Kaysar is sent over to the hammock and Ivette has to go to the gym. The entire house is then gathered into the living room several hours later after the four troublemakers have had enough time to cool down and giving a group warning about their behavior. Fortunately, this is followed by several honest apologies for their poor reactions and everyone making peace.
- Amanda Zuckerman thinking it was okay to threaten to slit someone's throat, especially considering the above example. Her threat was so malignant she caused an hour-long blackout on the live feeds where the producers absolutely railed her. But what the hell did they say!?
- Allison in US Season 9 ran into the diary room and started to tell people that she needed an epi-pen and to be sent to the hospital because she was having an allergic reaction to something. (Likely a Bee sting.) In the same day, Amanda fainted due to low blood sugar from eating slop.
- Some of Caleb's creepiest interactions with Amber in BB 16 entail this response, reaching their height in episode 10, as production even threw in the sound of ghostly music box tinkling. Another time, he seemed ready to snap at Cody for just talking to Amber and production added a Jaws-like menacing theme as Caleb looked on and later walked by in a huff.
- On Tuesday, September 20, 2017, during Big Brother 19, a mild earthquake hit the house. It caused the final three houseguests to head outside and wait for it to pass. Josh freaked out, since it was the first time he ever went through one, while Paul and Christmas braced for the tremors and helped calm him down.
- This turned out to be an aftershock of the much deadlier 7.1-magnitude Puebla earthquake. The houseguests would find that out only after leaving the closed environment of the Big Brother premises.
- Megan Lowder becoming so traumatized by the Big Brother atmosphere that she started having fits of vomiting and diarrhea, and cutting herself loose from the show so completely to ensure full healing that she is just gone.
- The instances in the UK run where contestants have threatened to commit suicide in the house and warranted the arrival of a psychiatrist or even walking off the show.
- Any incident where a contestant has an accident and gets hurt. The worst one on record is a broken leg.
- The infamous 'Fight Night' from BBUK 2004. UK viewers found this very unnerving to watch, they even had to call the police.
- 19 seems to be the year of the foot curse, where two women end up with heinous injuries to their left feet, Christmas and Raven. In only Week 2, Christmas has her foot severely broken when Jason drops her while roughhousing (for which he is infinitely sorry and ashamed of), and the injuries were bad enough to cause permanent damage. Christmas actually had to leave the house for a while to undergo surgery, where she had fractures in ten bones, one so bad she needed replacements from a donor. She has also been unable to compete in some competitions in the game and is looking at the end of her athletic career. Then, there's Raven, who got her foot injured the very next week, when she made the foolish choice of puttering around the house in just socks, slipped on the spiral staircase, and sliced open her left foot, requiring five stitches and causing enough bloodshed that she had to throw away her socks. Alex later comments during Week 7 that the spiral staircase is "death" after being forced to lug heavy camping equipment around in the middle of a punishment.
- Christmas' injury was so bad, she had ten broken bones, some of them distended out from the bottom of her foot; she even required an entirely new bone from a donor to replace a bone damaged beyond saving.
- The cute/creepy robot from Big Brother 20 has Uncanny Valley written all over its face.
- Good Lord Almighty, the first Veto Competition in BB 20 does something no other season in the US has done... it uses SNAKES. Real, actual, live snakes. Everybody panics. There's also the use of shock collars on the arms and legs that will probably have superfans reconsidering their desires to be on the show.
- A few times, rats and mice have actually gotten into the house.
- There aren't that many fights in the house that can really go off the rails, but one of them takes the cake: Bayleigh versus Tyler. It goes well past even the highest decibel yelling seen and heard from Janelle, Amber, Libra, and even Keesha combined. Bayleigh goes into a whole new category of angry that jumps right into crazy, as her temper is pushed so far over the edge she stops arguing and has a mental black out, followed by very high-pitched banshee-like screaming, as she collapses into a genuine meltdown and can only manage to howl the F-word and "I HATE YOU!!!". She also bit her lip in the middle of her screams and you can see a lot of blood staining her mouth.
- Sam Bledsoe, on a very off week when she's down in the dumps and emotionally troubled, explaining to JC what "stomp a mud hole" infers, and tells him it's a very bad thing and something you shouldn't repeat. She compares it to a curb-stomp, which JC also doesn't know. By this point in the game, Sam is exhausted and very pissed and not handling things well, and gives a very clinical description of it. The conversation takes a hard turn into incredibly disturbed territory as Sam casually explains the gory details of what a curb-stomp is, and Tyler's eyes go wide with shock. JC asks if this would normally kill someone, and Sam is hesitant to answer and dismisses any perceived approval of such violence. However, she does heavily imply that a curb-stomp can easily prove to be fatal. Then, and no longer wanting to talk about this subject, Sam walks out of the room, as if nothing was wrong and the conversation never happened. It leaves JC and Tyler speechless for several seconds.JC: (to Tyler) ...That was terrifying.
Nightmare Fuel / Big Brother