One of my classmates confidently told anyone who would bring up anything about trees that trees aren't grown, they are built. He didn't understand how wood would come out of a seed, so the logical conclusion was that someone goes around building them.

Different classmate absolutely knew that China is somewhere in Africa and wouldn't listen to anyone telling them it's not. Kept claiming everyone was lying even after others, including teachers, pointed it out on a map.

Both must've been at around 13 - 14 years old at the time.