I attended a reunion this past August in Fulda, Germany, with some of the folks from the 511th MI Company. As we were leaving a restaurant after dinner one night, we bumped into a traveling Bachelor Party that was making its way through streets of the city. They were already a few sheets to the wind, which undoubtedly explains why they appeared to think that I was a hilarious attraction. (I have that effect on drunk people, so it seems.)
Anyway, they were sounding off with a series of German idioms, and after each one they would laugh uproariously and ask me to join in. This didn't seem possible to me, as I hadn't lived in Deutschland for 30 years, and even then I had been a Russian linguist.
However, as luck would have it - somewhere in the back of my aging mind was the sole German idiom that I had managed to retain for all these years, which I recited to the assembled crowd:
"Freier macht die augen auf, heiraten ist kein pferdekauf!"
This had the desired effect - they laughed even harder than before, shook my hand, offered me a beer, slapped me on the back, etc. After offering me some pomme frites, (which were stored in the groom's hat - ugh), they bid me "Auf Wiedersehen," and they wandered off to continue their evening's festivities.
Unfortunately, that idiom loses a little in translation, (especially when using Google or Bing translate), but trust me - it's pretty funny for a soon-to-be-groom to hear. What it says, in essence, is: "Open your eyes, free man - getting married is not like buying a horse."
Nevertheless, it's nice to know that occasionally your long lost language skills can still come in handy.