I thought that in the song Bootylicious by Beyonce they were saying: "I dont think your ready for this chedder," when they were really saying "I dont think your ready for this jelly." I argued with my sister for ages before I saw the lyrics online...
A childhood belief about misheard lyrics

others believed things like this
- In Beyonce's song 'Crazy in Love', I always thought she said 'Daisy right now'.Anon
- I believed that if I ate Ready Brek, I'd glow like in the TV ad. — Why Aren't I Glowing?
- I used to believe that after eating Ready Brek I would glow, but that only adults could see it.— michelle
- When I was a child I used to believe that cows gave ready butter.— Bane
- I thought jelly fish were made out of fruit jelly. — Kevin
- i used to believe that red yellow and green meant "ready, set, Go!" on traffic lights..— cabagona