I used to think that the lyrics for AC/DC's "Dirty deeds done dirt cheap" were "Dirty deeds in the Dunder Jeep." I thought the "dunder jeep" was a cross between a jeep and a dune buggy, and pictured these people driving around in it committing crimes. I don't think I realized the proper lyrics until I was almost 20.
A childhood belief about misheard lyrics

others believed things like this
- a friend thought that the song "dirty deeds done dirt cheap" was saying "dirty deeds dunderchief"— dubs
- when i was younger i thought ac/dc's dirty deeds (done dirt cheap), was dirty knees and the thunder cheeks.— S
- Actual lyrics: "I've never been your beast of burden"
My lyrics: "I've never been your big suburban"
— Big Suburban - When I was little, I thought that Water Towers were full of dirty laundry. Why? I dont know.Anon
- When I was younger, I thought my brother kept eating my dirty socks, and that's why his feet smelled.— Kail
- I used to believe that toilets would open and swallow you up because they got dirty!!— swallowing toilet