According to Urban Dictionary, there is an actual word misunderheard. It means "when an individual fails to correctly hear what another individual has said". Do you suppose someone who is hard of hearing coined that word? The experience of having a misunderhearing happens often to me.
My latest lulu was when I misunderheard Avon (cosmetics company) for A-bomb (nuclear weapon). Conceptually, they are not the least bit alike! But if you remove the consonants from their pronunciation, they both have ay-ah vowel sounds. Darn consonants, they trip me up all the time.
Thinking about this misunderhearing later, I recalled a funny description I heard once of a woman who wore too much makeup: She had enough paint on to paint a battleship. And enough powder to blow her up!
Have you had any funny hearing mistakes or misunderhearings lately?