Idioms can cause a host of trouble when it comes to learning another language. For a good movie with a lot of this humor, check out Short Circuit and Short Circuit 2. The Indian character makes a lot of linguistic mistakes, mostly when it comes to his idioms, and it illustrates how ridiculous our language is.
For the real world examples, here are a few:
1. On Wednesday I taught at a local elementary school. One kid was missing from the fifth grade, and I overheard the teachers discussing it. I had a total language win when I caught them saying the word for chicken pox. I chimed in, proud that I knew what that was. But explaining the English version was less than intuitive. At first they messed it up with goose bumps. Then they wanted to know what a goose was. Unfortunately, that isn’t a word I know in Japanese. We all know that neither ailment has anything to do with birds, but explaining where the name comes from is rather tricky.
2. Today the teacher I work with wanted me to call upon a student to answer the grammar question. “Please pick up a student” he asked. I smiled at the image, especially when I caught sight of a kid who weighs as much as I do, but I didn’t correct the teacher, out of a wish to avoid embarrassment for him, and called out a kid’s name. It is possible I heard incorrectly, so I listened intently the next time. Nope, he didn’t ask me to pick OUT a student, he was still asking me to pick UP a student. I swallowed a smile and did so. It happened a third time too. Among my coworkers we often have debates about whether or not to correct such situations. Of all mistakes it isn’t that severe, and there isn’t a lot of freedom to correct superiors, no matter what country one is in.
3. Another teacher at a different school with whom I have worked consistently ends class with, “So much for today.” This fatalistic, discouraged view of the situation is in direct opposition to her sunny nature, leading the several of us who work with her to believe that what she means is, “That’s all for today.” But her mistake is so cute that I ordered my coworkers not to tell her.
4. Years ago, before I came to Japan, I worked at a coffee shop in the States. One of my coworkers was a German woman and one day she said something she regretted to a customer. “Oh,” she asked, “What is it called when you say something you don’t want to say?” “It’s called, ‘Putting your foot in your mouth.'” “In Germany we say, ‘I put my foot in a bucket of mustard.'” To this day I think of that. I don’t know why the Germans keep buckets of mustard handy, or who would put their foot in one, but it’s quite the imagery.