It's not really misheard as such, but in As Torches Rise, when Matthias sings "...how dark the night may seem", I'm always faintly suprised that he hasn't sung "how we danced the night away."
The whole of To Holmgard and beyong pretty much was mis-heard for me. The most convincing of which was "Set sail, for those rags and bones". Actually sounds quite a lot like that.
I'm really bad with lyrics actaully, most songs I can't understand over half of what is said.