When I learned German, that Kennedy quote made me laugh so hard!!
Still, if you risk learning a language, you WILL make such mistakes. On a ship, when my French was not yet so fluent, I asked for a sea sickness pill and mimed the motions of the waves going up and down. Sadly I had asked for a birth control pill, so the motions were oddly even more appropriate! (blush!)
My first day in France, I needed to exchange some dollars for francs. In my proud 6-years-of-high-screwel-French accent, I asked the first passerby, "Où est le banque?". Couldn't figure why they kept pointing to a bench in a nearby park.
Almost everyone who is learning spanish, and tries to say they are embarrassed, ends up informing their listener that they are pregnant! Embarazado - male pregnancy/Embarazada - the more common female pregnancy. :)