Today, I entered a bakery here in Munich and asked for "zwei brezn, bitte." I do not remember the exact German reply I got, but it translates (according to the baker) to:
I'll give it to you if we have it.
She explained to me that this is a Bavarian joke and her usual answer. To make sure that I had understood correctly, I asked if I was supposed to have laughed, and she confirmed.
What phrase is it likely that she used? The only word I'm completely sure that it contained is wenn somewhere in the middle. Note that I'm not just looking for a translation of the English phrase, but for the joke/rejoinder that is allegedly common in Bavaria.
Bonus question: How was that supposed to be funny?