When I was little, my older (and cruel) sister told me that the story line for the episode of Rugrats in which Chuckie eats a watermelon seed and a watermelon grows in his tummy was actually possible.
I still refuse to swallow seeds for fear that I might have a tree grow out of my ass.
A childhood belief about seeds

you weren't the only one
237 of you believed this
- i used to believe that if you swallowed the seeds from apples, trees would grow out of your ears!— Scott Davenport
- if you eat a seed, the plant will grow in your tummyAnon
- When I was little I use to belief that if we swallowed the pit of a fruit, a tree would grow inside us.— Maya
- when you eat the seeds from a watermelon a watermelon will start to grow inside your stomache.Anon
- I used to think that if you ate nuts and seeds that minature trees woudl grow in your stomach.— Gillian
- I used to believe that if you ate the pips in apples a tree would grow inside your stomach.— QueenB