In French 101, I once translated the phrase “la fête sauvage” a bit too literally. It means “A celebration of the wild”, but according to me, it means “A savage party”. Not too bad, except my classmates were all dirty-minded little bastards. 
I thank God that that is the most embarassing tale I have to tell.
A Russian friend of ours once complimented the food by saying it was “edible” instead of “delicious.” After the laughter had died down, we told him that he really didn’t want to say that as it sounded like an insult. Thereafter my dad would frequently refer to good dinners as being “edible,” a habit which I’ve picked up and have had to try very hard to refrain from doing when I’m with someone who’s not in on the joke.
I committed the “baiser” mistake. Exactly once.
My favourite one committed by another is when I offered some juice to my ex Éric and he said, no thanks, it’s too h’acidic.
Hassidic juice. I never let him live it down.
My ex-wife speaks six or seven languages pretty well (and reads two or three more, though it’s tough to find anyone to speak Old Norse or Old English with these days). Sometimes she got her languages a little mixed up, as when she was telling her French friend about her trip to Iceland, and told her about the beautiful foss she had seen there. In Norwegian and Icelandic foss means “waterfall,” but the word pronounced that way in French means “ditch.” Her friend didn’t think that was really a highlight of her visit…
In a Prauge gambling bar we were at very early in the morning, like 5 or 6, a drunk guy was complaining loudly about Czech President Havel. I tried to ask him “You don’t like Havel?” But instead loudly announced to the bar that “I don’t like Havel”, not an acceptable thing for a foreigner to be loudly announcing, and the worst possible place and time to announce it. I got many sideways stares from people at other tables who I suppose misunderstood that I had misspoken. Even the drunk guy quietly explained my faux pas.
A very common one I studiously avoided was saying vykourit instead of kourit: “to suck” (with a very sexual overtone) instead of “to smoke”. Many fights been started over someone innocently trying to ask a czech if they smoked.
Also, kure, “chicken” is very similar to kourim, to smoke. Once a man asked me for a cigarette and I told him I didn’t have any chicken. I liked that one so much I kept saying it.
I had been in Greece a couple of months and was just starting to be able to have basic conversations in Greek. I was eating dinner with my Greek boyfriend’s family on Οχι Day, a national holiday in Greece. One of the traditional dishes is σκορδαλιά (skordaliá), which is basically mashed potatoes with lots of garlic. Yum. They asked me what I thought of the meal, and I said I liked the σκορδούλα (skordóula). Σκόρδος (skordos) means garlic, and -ούλα (-oula) is the feminine diminutive ending, so basically I said, “I like the little female garlic.” Guess what my nickname was for the next nine months.
My ninth-grade Spanish teacher told us of a time she made a similar mistake…except it was to express embarrassment upon making a silly grammar mistake in a class, and she was dating the professor (a much more common thing in Europe than in the U.S., apparently, and much more accepted), and the other students all knew it…
The verb “visiter” is only applied to humans as in reference to f**king them. You can visiter a house, but if you visiter a friend, you must not have too much respect for them to refer to them that way.
A friend told me that she once was telling some business associates about herself, in French. She attempted to say “I have two cats” but used a slight variation on cat and announced “I have two pussies”. Much embarrassment ensued.
I made the “baiser” mistake quite spectacularly in France when I told one of the cousins in my French family, “Well, normally in the United States people don’t fuck their friends to say hello.”
Oy.
In Japanese, the word for “closet” is oshire, while the word for “ass” is oshiri. The look on my mother-in-law’s face when I told her where I’d stuck my jacket was perfect.
This one I said in English, but it almost got me in a lot of trouble. I was doing a demo lesson for a Japanese husband and wife who wanted to study together to prepare for the husband’s transfer to Singapore. We usually start the demos with casual conversation to gauge the student’s level.
Me: Do you have any children? (since dealing with schools overseas could be a useful subject to teach)
Husband: No, we don’t. Just us.
Me: Oh, ok, so do you travel a lot, then?
[silence… husband glances between me and his wife a few times]
Husband: No… we’re fine.
A few minutes later I realized that because ‘v’ and ‘b’ are pronounced the same, he thought I had asked if they had a lot of trouble because they had no children! I quickly tried to explain what happened, but I’m not sure if it worked. They didn’t sign up for a full course.
I’ve lived in Japan for 11 years and have made my share of howlers, but this is the all time best: I was telling a friend about a couple of cases of discrimination I’d faced (primarily being refused service for being white) when I declared “Gaijin mo ninjin da!” meaning to say “Gaijin are people to!” My freind said back in Enslish that I wasn’t. She said no, and I said yes again. Then, laughing, she said “But you don’t have orange skin or green hai!”. I realized I had just been insisting that I was a carrot (ninjin) and not a person (ningen).
Other funny ones include: Confusing eat and talk (taberu/shaberu) resulting in telling a friend I was going over to “eat” another friend instead of talking with him. And (while first studying, on the way back to the dorm; having just a learned a large chunk of food vocabulary) inviting a freind to a “yaki-gyu-nyu” party (burned milk) instead of a yakiniku (BBQ) party. Others include confusing or mispronouncing “shitake” mushrooms as “shitagi” (underwear) and “neko” (cat) as “Meko” (cunt).
When I was first learning Spanish, I couldn’t think of the proper way to say that I had to go to the bathroom. Trying to be creative and think some way to say it, I finally settled on Tengo que mearme; in other words, I have to wet myself (with the connotation of pissing on oneself).
Remembered a few more 
I had a hard time at first getting a hang of åäö in Swedish, so thats where the fox/asshole (röv/räv) problem came from in my earlier story. It also led to me not having any cards(kort) at all. I didn’t have an ID card, or a library card or a credit card. I had horneys instead (kåt). I had a bus-horney and quite a few other horneys too.
Damn, forgot the other one 
It will come back to me, or I will say something stupid again soon.
In German, the verb to Shoot and to Shit are quite similar.
Needless to say, my Aunt had a hard time understanding why I was shitting gophers all day.
An ex-boyfriend heard me refer to “Pins and Needles”. He woke up one morning with a numb arm and shouted “Ow Ow Penis and Noodles, Penis and Noodles.” I nearly died laughing, which he did not appreciate.
Just remembered another one: Leningrad, fall 1989 again. I was doing homework in one room of our dorm suite, and an American friend was in the other room, giving a lesson in American slang to my large, muscular North Caucasian boyfriend and several of his large, muscular North Caucasian friends. (A couple of mysteries in my life are 1. why I seem to find North Caucasians passing through my life in the most unlikely spots, and 2. why they are all built like Olympic wrestlers. Not that I’m complaining, you understand!) Much laughter was emanating from the other room, and it was actually quite annoying, as I was trying to concentrate on some rather difficult literary passages.
After a while, the American friend yelled for me to come into the other room. I told her that I was studying, and couldn’t it wait another half an hour? She promised me it would be worth my while. I finally did, and was treated to a semi-public recitation of my boyfriend’s newly learned slang phrase, which was “How about a quickie?” Then his friends all tried to repeat after him in unison, but it came out more like “How about a cookie?”
I still can’t decide which would have been more incongruous: group sex with a bunch of semi-devout North Caucasian Muslims from small villages, or the idea of that very macho group baking me cookies.
I mainly speak just English, however Romani words slip out sometimes.
Like the time I told my MIL that I’d be round to see her later, but used the Romani word for see - Dik. The look on her face was priceless.
gasp choke help… can’t…stop… laughing… gasp
In third grade at the International School, our (American) teacher wanted to learn some Finnish, so my friend and I started teaching her the numbers from one to ten. Naturally, it was funny for us eight-year-old native speakers to listen to this authority figure wrest and wrangle her way up to five.
In Finnish, whether a word has a single or double letter can alter the meaning quite a lot (“mato”=worm, “matto”=carpet). Six in Finnish is “kuusi”. “Kusi”, however, means “piss”. I was so scared that I was going to laugh out loud at my teacher. When she asked why we were giggling, we have some desperate explanation like “kuusi also means fir tree and it’s funny”… :rolleyes:
Ah, the memories…
I knew a Japanese lady who had married a G.I. after the war, and she had a hell of a time at first because he didn’t know Japanese and she didn’t know English.
She’d seen an American movie where somebody said “Hey, buster!” or something like that. So she’s in a store and this guy accidentally dropped some money. She picked it up and said “Hey bastard, you drop your money!”
The first time she ate in a western restaurant, she ordered the only food she could remember the English for: t-bone steak. She had no idea what it was. They bring her out this huge hunk of meat, with knife and fork (she only knew how to use chopsticks) So here she is trying to attack this steak with sharp utensils she never used before. She dug in and tried to cut it and it went flying across the room.