Sure, there are basic things like Santa (well, for lots of people, but not me and my sibs), but I know we all had crazy stuff we believed, too. Share it here!
  1. Walt painted the world
    I think it may be normal-ish for kids to think the world used to be black and white. All the old movies and shows are B&W after all. But once I saw a picture in a book of Walt Disney on a ladder painting a wall. It just suddenly was clear to me that the world wasn't black and white anymore because Walt painted it! I'm not sure how long I believed or when I stopped, but it was a magical time. (Sadly, I googled a bunch to find that pic from that book and couldn't find anything.)
  2. This may be a little different than what you're asking, but when I was in kindergarten, I believed that the (yearbook) photographers that showed up at recess to take pictures of us must be up to no good. From all the 80s PSAs about stranger danger, I was very concerned. I hid in the treehouse and told other kids not to let them take their picture!
    Suggested by @erinflusche
  3. For at least a decade I believed that I would die at age 24. It wasn't worried about it at all. I just knew this was how it was supposed to be. I kind of forgot about it in my late teens. When I turned 25 it hit me that I hadn't died. I was ecstatic! Ever since then I've felt like I'm on bonus time, for free!
    Suggested by @pili_ervin
  4. I believed that any time you played a movie, the actors had to drop what they were doing, run to the studio, and act out the whole movie for you. I was always amazed by how consistent their performances were. This also kept me from playing movies late at night or early in the morning out of respect.
    Suggested by @hannahbee