In Queen's 'Flash Gordon' theme, there's a bit where the evil queen (or whatever she is) does a talkie bit. I always thought she was saying 'Dispatch Warlock and Ajax to bring back his body', whereas my sister always believed it was 'Dispatch Warlocken agents to etc etc'. The dispute went on for years, until she met her future husband, who kindly pointed out that the actual words are 'Dispatch war rocket Ajax to bring etc etc'. Neither of us believed him, until we saw the film and discovered that there was indeed a rocket named Ajax in it, whereas there were no warlocken agents and nor were there any characters by the name of Warlock. Oh well, at least I got the 'Ajax' bit right.
A childhood belief about misheard lyrics

others believed things like this
- I used to think that James Bond and all the other secret agents worked for MFI.— John C
- When I was child I used to believe the future going to be similar like in the film Back to the future part 2 — Frankie
- I used to believe that my mum was the queen. She does look a bit like the queen... minus the orb and sceptre.— Vix
- I used to believe that cars were propelled by their exhaust like some kind of rocket.Anon
- I used to believe that rocket ran on gasoline and that in order to save gas, we should end the space program.Anon
- I used to believe that the exhaust fumes coming from a car were actually what pushed it forward like a rocket — rocket car