I once saw an illustration of bird flight in a book and for a long time I thought there were separate breeds of geese called 'upstroke' and 'downstroke'.
A childhood belief about birds

others believed things like this
- When I was little, I thought the singular form of geese was "gee"— Kate
- My favorite excuse:
Must be those trouser geese again!— Tootie Fruity - I used to believe "mixed breeds" of dogs were made by two dogs being put in a blender— Andie
- I used to believe I could fly.
All I had todo was step of a flight of stairs and I'd be walking in the air...— Dolly - I used to think a female daddy-long-legs was called a "mummy-long-legs".Anon
- I once for some reason thought a Mantis was a bird, instead of a bug...— Laurie J.