When I saw ads for toys that said "batteries not included" I thought it meant that the toy didn't need batteries to work. When I asked my parents for a toy I would ad "batteries not included" as a selling point, becuase then they wouldn't have to buy batteries.
A childhood belief about toys

others believed things like this
- my nephew used to believe that when people died, they just needed new batteries.— p-daddy
- I used to believe that I could make a laser by putting more batteries in a flash light.— Tyler
- I used to think that putting batteries in your ears could electrocute your brain. Hahahaha.Anon
- I used to suck on the ends of batteries intent on gaining super electric powers. Anon
- I similarly thought that "Proud Mary" included the lyrics "pumped a lot of tanks down in New Orleans."— Larry
- I used to believe that the disposable BBQ's had the meat displayed on the packaging was included inside. — Raggamuffin