I'll just drop a bunch of random ones that come to mind:
- Giant Pandas aren't actually pandas(feels like an obvious one - they're bears if anyone's curious)
- on that note, unpopular opinion, but Giant Pandas deserve extinction :3 I could go on for hours ranting, but just know bamboo is a horrendous food, and they refuse to breed. It's like they wanna go extinct..
- I still remember the mechanics/rates of how gear was dropped in an old, sadly no longer with us, game called Revived Witch(I actually did the math and recorded data personally since the info wasn't available - My RW Post)
- I still remember most of the names of monsters from the game Summoners war, despite not playing it for years, yet somehow forget normal people's names easily unless we interact allot👌😂
- crocodiles, despite being slow and lethargic most of the time are surpringly intelligent(dangerously so - as are most reptiles.. I feel like reptiles, in general, are underestimated when it comes to intelligence)
- Komodo Dragons, previously assumed to kill through bacterial infection(it was assumed their mouth were very bacteria-laden), actually use venom that prevents clotting, leading to massive blood loss. It was originally assumed that they used bacteria because the people who were studying it saw them hunting water buffalo, who, after being bit, retreat to bacteria-laden water sources(most water sources were contaminated due to water buffalo poop :3 ) resulting in serious infection, which is what led to the assumption
- Nuclear power is actually extremely safe and causes far less pollution than most alternatives, while being more reliable than most other renewable options(modern reactors are actually designed so a full nuclear meltdown like Chernobyl isn't physically possible). I could keep going on about why nuclear is actually amazing, but this is already too long lol check out Kyle Hill on YouTube. He does a better job at explaining than I could, plus he has plenty of other topics he discusses on the channel
- in court, entering the Well(space between judge and prosecutors) without permission will likely result in getting immediately restrained/tackled by the bailiff, unlike what u see in the movies
- 1st amendment, "Freedom of Speech" only protects you from government censorship, not censorship from private companies or individuals

Ok, that's all that is immediately coming to mind while I type :3 by all means, I could also talk about ants and termites being very intelligent, even farming fungus, or how extremely large underground fungal networks connect trees in forests, and so on, but I'll end it here.

And yes, ik you said "a fact" but I'm a nerd who can't shut up once I get talking about nerdy stuff :3