I used to believe that the Chumbawumba song 'Amnesia' said "Do you soccer punch long-term memory loss?" when it was actually "Do you suffer from long-term memory loss?" My father heard me sing it once and laughed so hard he cried... and still wouldn't tell me the correct lyrics.
A childhood belief about misheard lyrics

others believed things like this
- I used to believe that a "punch line" meant a line of people waiting to dip punch from a punch bowl.— Sheila
- I used to believe that peanuts were a daily must to strengthen the memory like elephants — Qb Cheese
- I used to believe that the term "being mugged" meant someone beat someone else with a coffee mug.— Matt Thiel
- I thought the term maiden name actually applied to women who were maidens.— Natasha
- i used to think that the term 'necking' referred to boyfriends and girlfriends who rubbed their necks togetherAnon
- I thought that soccer moms were moms that played soccer!Anon