On Death Cab for Cutie's expo 86 (or whatever it's called), I thought the line, "as if you held in your hand a smoking gun, and on the floor lay the one you loved" was really "as if you held in your hand a smoking gun, and on the four-legged one you loved."
Also when it said "familiar resolve" I thought it said "familiary's song". Not quite sure what I thought a "familiary" was...
A childhood belief about misheard lyrics

others believed things like this
- My teacher held out a hand to say, "stop" but I thought she wanted a high-five.Anon
- I thought that smoking pot involved an actual pot from the kitchen.— Aeris
- I thought the line in the song "more than a woman" was "four-legged woman".— boo
- A friend on mine thought that smoking menthal cigarettes would make his breath minty fresh.Anon
- I used to believe that Marijuana was a disease you got from smoking.— LMH
- For a while, I thought hand grenades were called "hen grenades" and they were made of rotten eggs.— Athazagoraphobia