In Macross Frontier, this was in fact the entire cause of the show's central conflict. The Vajra, being Bee People, didn't quite get humanity's whole 'individuality' thing, and assumed our lack of clear, unifying purpose and direction to be the result of a catastrophic breakdown of our Hive Mind. Being nice, altruistic types, they decided to rescue the being they believed to be the human Hive Queen, Ranka, and the rest was history. To their credit, though, they eventually realised their mistake, and even went as far as to sacrifice millions of their own to prevent the Frontier fleet from being obliterated by the Big Bad before offering them a place to stay on their homeworld.
In Majin Tantei Nougami Neuro, this trait subverts Too Spicy for Yog Sothoth: the (arguably) main character came to the human world because if he'd stayed in the underworld he'd have died of starvation. Basically, he feeds on the energy that makes people do crazy and wrong things like premeditated murder, and there's plenty of that. In the early manga, he's focused on trying to find food, but then the really crazy people put their plans in motion and he basically has to save humanity to protect his food source. He specifically states that he's not capable of understanding humans because Humans Are Insane, too.
Insanity is a huge theme in Soul Eater, with numerous characters losing their minds at least once throughout the series, whether it's because of the black blood, Asura's influence, or in the case of people like Dr. Stein, already being insane to begin with.
The Joker: Faced with the inescapable fact that human existence is mad, random and pointless, one in eight of them crack up and go stark slavering buggo! Who can blame them? In a world as psychotic as this... any other response would be crazy!
Several of the Joker's more notorious schemes are attempts to prove this is true to everybody else — and maybe to himself. Otherwise, he'd have to face the possibility that maybe the world isn't crazy... that maybe it's just him.
In No Gods, Only Guns, humanity is generally considered batshit crazy by the Citadel species. There's a good reason for it; rampant genetic experimentation by the various Mega Corp. superpowers upon the human genome has resulted in wild mutations, with insanity being a common side effect of the more physiological-altering effects. As a result, you get a human race that thinks shotguns that shoot rockets and personal shielding systems that create giant explosions when they collapse is not only viable, but preferable.
Men In Black: This could be why human thought is viewed as an infectious disease by some aliens. No wonder they don't want us to get our hands on a Universal Translator.
In the direct-to-DVD sequel, Starship Troopers: Hero of the Federation, the Arachnids (or Bugs) use this as a justification for attacking and taking over humanity.
Control Bug (speaking through a human): Poor creatures. Why must we destroy you? I'll tell you why. Order is the tide of creation. But yours is a species that worships... the one over the many. You glorify your intelligence... Because it allows you to believe anything. That you have a destiny. That you have a right. That you have a cause. That you are special. That you are great. But in truth, you are born insane . And such misery... cannot be allowed... to spread!
In Avatar, when telling Jake he will be taught the ways of the Na'vi, Mo'at says, "We will see if your insanity can be cured."
Spoken word for word in Stephen King's horror film adaption of The Mist when unstable Mrs. Carmody takes over the grocery store with her group of desperate followers and makes increasingly terrible demands while Eldritch Abominations lurk right outside the windows, as part of the main theme that humanity would automatically drop all the rules when thrown into the dark.
Ollie: As a species we're fundamentally insane. Put more than two of us in a room, we pick sides and start dreaming up ways to kill one another. Why do you think we invented politics and religion?
When it comes to humanity, the other species in Farscape have a sample set of one, and may not fully grasp that Crichton doesn't really meet our commonly accepted definition of "sane". His constant Earth pop culture references that nobody else could possibly get surely can't help.
This seems to be a common view by the vast majority of Stargate's aliens, granted even the transplanted humans seem to think this of the Tau'ri. Though this may reflect mostly on Stargate SG-1... okay, mostly on Jack.
Values Dissonance can leave modern readers with the interpretation that it is the humans portrayed in the works of H.P. Lovecraft who are insane, being so fixated on a ridiculously dull, narrow-minded view of the universe that any exposure to the fact that they don't know everything there is to know about the universe and/or are not inherently gifted above even other branches of the human race causes them to end up going mad.
Explanation: the Sun is about to go nova so humans ALL got on rocket ships to find a new sun, knowing how crazy that would be. Aliens find us mid-journey. They might regret that.
Stephen King is fond of this trope, as the quote shows. CELL discusses it - Clay theorizes the phone didn't drive the humans insane - it simply wiped everything out, and the psychos everywhere are simply base humans doing human things. Like stabbing everything. Another character puts it simply:
"We didn't survive as a species because we were the toughest, or the smartest. We survived because we were the most murderous, craziest fuckers in the jungle."
In the Animorphs companion book Visser, Edriss comes to this conclusion after infesting her first human. Several other books suggest that when the Yeerks jumped at the thought of a Class Five species (lots of useful bodies that didn't have the tech level to fight back), they had no idea what they were gettinginto.
In The Visser Chronicles, Visser One was shocked when she first entered a human mind, because it had the ability to doubt itself, seeing this as insanity at best. She stated that living with our own traitor in our heads was something completely alien to her, and was why we went to war with other members of our species, even committed suicide - another unfathomable concept.
However, she also recognized the major advantage of self-doubt: decisions made when you can question your own thoughts tend to be wiser and more useful in the long run. This may be why humanity gains technology so quickly compared to other races.
There are severalwaysto interpretThe Damned by Alan Dean Foster, but in terms of tropes on this site this might be the best way to describe its portrayal of humanity. Humans evolved on a planet that shouldn't have been able to support life, in a way that shouldn't have produced a sentient species, and while as individuals we're usually decent, we display disturbing tendencies in our speech patterns and our art that are magnified when we're in large groups. We're also immune to Mind Reading, with spectacular results any time it's tried.
The Lepar, normally considered the least intelligent of the fully sentient species in the Weave, are immune to the countereffect resulting from using mind reading on humans. Because the Lepar can counterbalance the negative influence of humans, humanity is finally fully integrated into the Weave.
This is the conclusion drawn by Wonko The Sane in So Long, and Thanks for All the Fish, who decides the world has gone mad after seeing detailed instructions on a package oftoothpicks. He then creates the Asylum, which contains the entire world except for his house, which he turns inside-out and declares "Outside the Asylum". He spends much of his time patiently waiting for the world to end, unaware that the world already ended three books ago.
The Race of Worldwar`s reaction to half of what humanity does is "Madness!"
Letter to a Phoenix ends thusly: "Only the insane destroy themselves. And only the phoenix lives forever." All other sapient species in the galaxy grow moribund and die out, but humanity survives because it periodically comes within a hair of wiping itself out. (The near-immortal narrator still hopes we never again get as far as the civilization that planet-busted the world between Mars and Jupiter, though.)
The Canim consider humanity to be insane as well, but not in a good way. When Tavi is attempting to negotiate with Nasaug to have the Canim leave Alera peacefully, he points out that the both sides are going to suffer needlessly if they fight, as the Alerans want the Canim gone and the Canim want to leave. Nasaug agrees, pointing out that in a rational world, this would happen. However, he says, they are in Alera.
Interestingly, Kitai says in the third book that she also thinks the Canim are insane, if not quite so insane as the Alerans. It's the convoluted internal politicking both groups engage in that she finds so irrational.
Bruce Coville's My Teacher Is an Alien series uses this trope, which is rare for a children's story. Humans are potentially the smartest creatures in the galaxy (due to 90% of Your Brain ), but also the only ones stupid enough to have war and poverty. Turns out that all that extra brain matter was there to grant us telepathy long in the past. When there were too many humans, there was too much "noise", and we instinctively suppressed this ability to protect ourselves. Losing that power left us traumatized as a species, with both an inherent desire to come together and a need to stay apart, and resulted in us being somewhat sociopathic.
Discworld approaches this at times. It's most explicit in Thief of Time, which portrays a "dangerously sane" character as effectively inhuman. The reason most of the Auditors go Ax-Crazy when Humanity Ensues is because they're fighting their insanity, rather than trying to work with it.
Night Watch uses the same recipe; Carcer Dun is not, technically, insane. It's merely that he's realized that all those little rules that keep society ticking over nicely only apply to you if you let them, and therefore the only thing between him and murdering a coach full of accordion players for shits and giggles is his own inhibitions. He is, in fact, more in tune with objective reality than the average man on the street; a sort of inverse psychosis if you will.
In David Weber's Out of the Dark, the invading alien Shongairi are confused and flabbergasted by humanity's continuing resistance against them even after they've killed half of Earth's population. They eventually realize that, by their own standards, humans are clinically insane. The Shongairi, being a pack-based carnivorous species, have a psychology focused on pack-mentality, with the rest of the pack submitting instinctively to the strongest "alpha" once s/he has demonstrated superiority. All other species they've encountered are herd-based omnivores or herbivores, who will submit to deflect violence away from the herd as a whole. However, humans are family-oriented instead of pack- or herd-oriented, and as a result the act of bombarding entire cities off the map and killing half the population just pisses them off. Since the need to protect family overrides submission, and pure, undiluted hate due to harming or killing family drives humans to keep fighting regardless, the humans come off as completely insane to the Shongairi. Also, one of those cases where it works.
To the Moties, humans are all "Crazy Eddie", because we refuse to accept that some problems just can't be solved and persist in trying to Take a Third Option.
Larry Niven's Puppeteers are absolutely single-mindedly focused on self-preservation. The Kzin see them as unbelievable cowards. Humans just think they take it too far, to the point of neurosis at best. But the Puppeteers think the rest of us are absolutely nuts for not being the same way. After all, what other priority can possibly ever be more important than self-preservation? (Kinda makes sense when put that way, huh?)
At one point there's a discussion of the concept of humor, which the Puppeteers basically lack. The human is surprised: "But I thought humor is associated with high intelligence, and you're so advanced...?" The Puppeteer says, "No, humor is associated with a disabled defense mechanism." (Also makes sense: when you're laughing, your situational awareness is impaired and your breathing pattern is disrupted, making you less ready to respond to a sudden threat.) It continues: "No sapient being ever disables a defense mechanism."
Later, the human notices an odd mannerism: the Puppeteer (which has two heads, each with one eye, on long flexible necks) sometimes responds to things he says by turning its heads inward so its eyes are looking at each other. He interprets this as a kind of laughter equivalent. (When the eyes are looking at each other, they're not looking outward. A disabled defense mechanism?)
The Foxen general opinion of humanity in The Red Vixen Adventures, partially because they have a lower rate of mental disorders than we do and because they think our obsession with democracy is funny. But the Foxen are poorly equipped to treat the few who do develop mental disorders, one main character has PTSD from an abusive spouse and only shows signs of improvement after her family brings in a therapist from Earth, and her ex was simply locked up in an asylum.
The group Puzzlebox has a song, appropriately titled "Nuts," about an alien scout's observations of our species.
They're nuts, I say, Commander! Their heads aren't screwed on right.
The bird of wisdom took one look at them and then took flight!
As near as I can tell, they just get by on luck and guts.
I've studied them, and I should know, they're nuts!
One Calvin and Hobbes comic has Calvin ask Hobbes, whilst narrowly missing several dangers on a sled, whether he thinks people are "basically good...basically bad...or just crazy".
Calvin(buried in the snow after a crash): You know, it's very rude of you to keep changing the subject after every sentence.
Hobbes: I choose crazy.
Warhammer40000 has this in spades. While every race in the setting considers every other race to be some flavour of crazy, humanity come right out and owns it.
Thought for the day: Only the insane have strength enough to prosper. Only those who prosper truly judge what is sane.
The Bioshock franchise is stock full of these. No matter how good the intentions of its creator, Andrew Ryan, the city of Rapture delved into unethical human experimentation and chaos not long afterward (part of it caused by Ryan abusing his power). Later, Sophia Lamb and her cult following came along, hoping to eradicate the ego or self that is responsible for human evil... by forcibly experimenting on her own daughter in hopes of creating the ultimate altruistic being, deprived of free will. And BioShock Infinite takes place in a fantastic city floating in the sky constructed by the U.S. government as an icon of hope to American ideals, everything goes to shit when the city breaks contact and disappears for a decade after blowing Peking all to hell in response to American hostages being taken during the Boxer Rebellion. By the time you get there, it's turned into a Crapsaccharine World on the brink of a war between a racist, jingoistic cult that worships George Washington, Benjamin Franklin, and Thomas Jefferson (the Founders) and murderous Bomb-Throwing Anarchists (the Vox Populi). Ironically, probably the only truly sane people you ever encounter are the forcibly brainwashed protagonists.
The Reapers believe that anyone that knows of their existence and power but still opposes them to be completely outside the bounds of logic. Paragon Shepard tells Harbinger to shut it in the Arrival DLC for Mass Effect 2.
Shepard: Maybe you're right. Maybe we can't win. But we will fight. We will sacrifice. And we will find a way! Because that's what humans do!
Considering the amount of horrifying and traumatizing shit Isaac Clarke is forced to go through, he's arguably a lot safer fighting the hideous undead Necromorphs than he is deciding which humans he should trust as they are likely to be (1) unlucky people driven insane by the Marker, (2) EarthGov like Kendra Daniels, or (3) deluded or conniving Unitologists in the form of Daina or Challus Mercer. Good, sane people are few and far between out in the black, with a good half of them either horribly killed or driven bonkers by the Marker.
"When Humanity joined the Gallimaufry, the first impressions of established idea sifters were rather disappointing. Yes, they were entertainingly crazy, but their quirks were mere amplifications of other neuroses and psychoses that had been in and out of vogue for millennia."
Humans are noted for being the first species in the history of the universe to invent popsicles. Freezing liquids on sticks? And then eating them?? Madness!
Coyote thinks that the ability of humans to imagine and believe, creating mythical spirits (like Coyote himself) and giving them power through their beliefs, is indicative of this. And yet, he also admires the human ability to see beauty in everything, "even a flame!"
In the Veil of Madness stories from 4chan's /tg/, this is explicitly the reason why humans have free run of a good chunk of the galaxy - Part of it drives anyone in it insane, but humans are all a little crazy already.
Though this is more of an inversion, since many of these diseases were classified as such so that patients could more easily bill their health care providers for therapy. In other words, insanity was defined in such a way that it would encompass the vast majority of humans.
In other words pretty much everyone has been depressed at some point in their lives. Problems is that for some people that never goes away and robs them of the desire to do anything. Including living.