Wasn't until I was 21 when I drank Lactose-Free milk and DIDN'T go sit on a toilet for an hour that I realized I am lactose intolerant. I thought it was normal to have stomach cramps after drinking milk. -u/xeredge

That roadrunners are not the size of an emu. -u/PURKITTY

That horse poop contains hay that comes from the inside of the horse. For the longest time (24 years) I thought that someone would put hay over horse poop to cover it - similar to picking up after your dog. I never really thought about it much beyond that. One day, I was backpacking and wondering why someone would cover up horse poop in the middle of the wilderness. Then it clicked - horses eat hay! Horses poop hay! I felt like an idiot that day and still do! -u/emj159753

I learned how to ride a bike at the ripe age of 24. -u/newhvac

That “rolling your eyes” isn’t fully making a circle with your eyeballs. -deleted user

I thought the D in Disney was just some random symbol, kinda like a backwards G. It took me until like 7th grade to realize it and even as an adult I still can’t unsee the backwards G. -u/Death-By-Lasagna

That sodas were called soft drinks because they had no alcohol lol. -u/zejus_christ

Corned beef wasn’t made by cattle that were strictly fed corn. My mom couldn’t stop laughing. -u/Ilikestarwarstoo

Ponies are NOT baby horses. -u/phrygN

That if you wear a white bra, you can see it through a white shirt. But if you wear a nude-colored bra, you can’t. I was 40 when a coworker shared this with me. -u/midwesternvalues73

I thought an armadillo was a reptile rather than a mammal. -u/failurebeatssuccess

That Abuela and Abuelo were not my Cuban grandparents' actual names. -u/MarzipanJoy-Joys

So. Many. People. Do. Cocaine. -u/LaborRelationsGuru

At roughly 37, I learned pineapples grew from the ground. Not from a tree. -u/Human_Watch4506

That narwhals are real. I thought they were cute mythological creatures, until I saw a brooch a friend had and asked if it was part of the companies mythological line. She asked me if I thought narwhals were myths, like unicorns. I laughed and said of course they are. I was 35. -u/katikaboom

"TP" stood for Toilet Paper. I thought to "TP someone's house" you just put toilet paper over it to look like a teepee. -u/crusoestudio

It’s “for all intents and purposes” not “for all intensive purposes.” -u/charlessturgeon

That our next door neighbors were lesbians and not just “good friends." Lovely people. Didn’t figure it out until I was in college. -u/secretbaldspot

That pufferfish don't use air to inflate. -u/skewed-perceptions

That you can flush used toilet paper. Parents taught us as kids to throw away the paper in the trash can for fear of backing up the toilet. Wasn’t until college that I realized my parents were accustomed to that method because they had sh*tty plumbing where they grew up in Central America. -u/fuckintacos

That those funny X-rays of odd objects inside of someone is not as a result of someone swallowing it whole. -u/raspberrypigeon

I thought everyone’s mouth got itchy when eating bananas. Almost 40 years old and find out I’m somewhat allergic to them. -u/tbr6742

That I needed glasses. At age 21 my friends were hassling me about being dyslexic because I kept getting words mixed up (second year at Uni). Until then, I had just been reading by looking at the shape of words and guessing the words based on the context and wider story. I had been reading this way for years and survived Uni before finding out my prescription was +1.50. The optometrist said it was amazing I hadn’t noticed. When I put the glasses on, everything was in 4K Ultra. I can now see individual letters. -u/CasualPhilosopher25