Some time ago I was watching a movie and heard someone address another character affectionately as “mopty Jew” (I’m not sure but I think it was Maurice Chevalier in Gigi.) It wasn’t until much later that I realized that what he’d said was, “Ma petite chou”, an endearment meaning, I think, “my little cabbage”. Yes?
Anyway, what other foreign words and phrases have you heard (or mis-heard) that puzzled you at first, but finally you figured out what it was they were saying?
hors d’oevres.
I swear, I thought it was spelled “orderves” for years. When I first saw it in print, I had no idea what a “whore’s dweevers” was.
Then again, I thought “annihilate” was spelled “iniolate,” too.
I thought in the theme song for Speed racer they were singing Dopey Race, Dopey Racer, Dopey Racer, Go!!
Peter Gabriel’s “Games without Frontiers”
Part of the refrain is jeux sans frontieres,
which is french for “games without borders”
but for years I couldn’t figure out what they were singing.
“She’s so funky, yeah” ? That never made sense.
I kept trying to figure it out, in my american english-centric way never thinking that it might be a different language (and I’ve even lived in France!). Finally, I bought the CD and read the lyrics. Ahaa! (Not to mention “D’oh!”)
Later I was talking with this rather pompous guy I knew and he sang it as, exactly, “she’s so funky, yeah.” I wanted so to make fun of him for this, but of course I couldn’t possibly justify that to myself, so I politely told him the correct lyrics and the translation.
My own small contribution to fighting ignorance.
I sang “She’s so funky yeah” too!
Also in Beck-LOSER:
Correct: soy un perdedor, I’m a Loser baby"
Wrong: “Oh, in Benidorm, I’m a Loser baby” 
I always sung the “soy un perdedor” part as “so I’m a Labrador”
I always heard “jeux sans frontieres” as “she’s so popular”. I had no idea what the real words were until I saw them in a misheard lyrics thread on some newsgroup.
This is kind of the same thing.
Due to a multiple year brain fart it took me the longest time as a kid to realize that the actor I had always seen in credits as Lawrence Olivier(which I thought was pronounced like Oliver in Oliver Twist ) was really the same guy as the Sir Lawrence Olivier(Oliv-e-a) that everybody always talked about.
Are you sure it wasn’t “ma petite bijou”? (Meaning “my little jewel”, with connotations of being small, pretty, decorative, etc., without being particularly valuable).
“Ma petite choux” does mean “my little cabbage,” which is a term of endearment in French, much like “honey pie” or “sweetkins” is in English.