A misbelief is same as a myth, but it is usually made by people around you. A myth is something you heard and took it for a fact, while a misconception is slowly induced.
The 24-hour rule
Maybe you have seen in many movies that you have to wait 24 hours before being able to report a person as missing. But this is not true! You can report it any time, as long as the absence is an unusual one, not being late for lunch ten minutes after school. This is more like missing from home or your bike is found lying by the side of the road but you are nowhere to be found, not answering phone calls.
Origins of fortune cookies
Fortune cookies are associated with China, but in fact, the initial concept is Japanese. They are associated with China for us, Europeans because China is closer to us than Japan is. See here how I compare more things like these.
420 is a popular number, which is related to marijuana. In Los Angeles, 420 is the penal code for marijuana use. But this number did not originate from the penal code. It is originated from the Californian police code 420, which prohibits public disturbance. Its use started after 4:20 P.M, when a group of students got caught smoking weed. The reason why this is where the number originates from is that this happened around 1970, much earlier than the appearance of L.A penal code 420.
Waking a sleepwalker
It is said that waking up a sleepwalking person might cause them brain damage or worse. Actually, this is not real. In fact, if a sleepwalker suddenly wakes up, he might be confused or scared and might try to hit you, but will not become violent, faint or die. I also sleepwalked once and woke up because my alarm clock rang, which is sudden, and nothing happened.
Aircraft toilet waste
There are mentions saying that plane toilet waste is thrown outside the plane, while it is flying. No! It is actually stored in a tank and disposed on the ground. Old trains also dumped waste on tracks, but modern ones have tanks.