I've generally got a good ear for lyrics but for the longest time I thought the that Dobie Gray was singing "give me the beach boys and free my soul", instead of the actual lyric, "give me the beat, boys"
My younger brother was for years convinced that the Sex Pistols' lyric "another council tenancy" was actually "and other c*nt-like tendencies". Really, though, that's a pretty forgiveable mistake. I doubt most teens in middle america know what a council tenancy is and my brothers version certainly sounds like something Johnny Rotten might say.
A childhood belief about misheard lyrics

others believed things like this
- I used to believe the Beastie Boys were a boy band. Well, the name sounds similar to Backstreet Boys!Anon
- i could swear eleventeen was a number for the longest time -- it still sounds pretty convincing.— erin
- i was afraid to use my dad's hairbrush because i thought it would give me gray hairs.Anon
- I used to believe that the lyrics to Bon Jovi's "You Give Love a Bad Name" were "You give love a Band-Aid".Anon
- I thought the lyrics to "We're going to Ibiza" by the Venga Boys was "We're going to eat pizza"— ShannonOfDoom
- i thought that you had like a box or something inside you to hold your soul for the longest time— jill