I used to believe that St Pancras station was actually St Pancreas. It wasn't until I was corrected - at age 21 - that I realised what I was saying...
A childhood belief about trains

others believed things like this
- I used to believe that horses laid eggs. No one ever corrected me...— kelly
- I thought your loins were kidneys, and nobody corrected me until I was a teenagerAnon
- I used to believe that the Fire Station was where all fires occurred.Anon
- When ever we went to the gas station, it was to replace the blinker fluid.Anon
- I used to wonder how they managed to fit the orchestra into the radio station.
— sally - My sister used to think that there was an oil well under every gas station that led directly to the gas pump.Anon