"How come then when Herr Flick and Helga are discussing how to kill the general (the katarri death pipe...) Rene' is spying on them through the keyhole and he seems to understand everything perfectly...."
This is a good point, which brings to light the oddity about the languages I have been wondering myself.
If the accents denote languages, then it doesn't make sense for "Herr Flick of the Gestapo" to speak in german accent ALSO when he is disguised as an onion-seller! Wouldn't everyone be suspicious of an onion-seller that speaks GERMAN ONLY? (Not to mention Helga addressing him as "Herr Onion-seller"..)
And it would seem quite weird that the conversations between René and the german officers would be held in two languages simultaneously (wouldn't that become increasingly confusing, especially since two languages won't have the same idioms and ways of explaining things, etc.?), instead of just speaking the one language?
I mean, if René understands german, why doesn't he just speak german with the german officers? Wouldn't he want to please the 'conquerors' anyway? I mean, even when his life is at stake, he still speaks in a french accent!
Otherwise it seems to make sense, and is done very well, but this german-french-bit leaves me puzzled indeed. It seems to be either
1) The germans speak german, and René understands german but still chooses to use french to speak to the german officers (which would be confusing, illogical, disrespectful and odd)
2) Both parties speak french (in which case, the german accent makes NO sense)
3) Both parties speak german (in which case, the french accents makes NO sense)
Is there a fourth possibility, or didn't the writers simply think this through?