I once bought corn from Hokkaido that I proceeded to cook, and kept asking my boyfriend to pass me the コウモリso I can put it to boil.
He kept looking at me confused until he asked what I was talking about. I pointed at the corn and he said ‘You mean ともろこし？’ 
So I asked what was コウモリ then, that’s when he told me that’s the word for bat 
.
Not gonna lie I laughed my butt off on this one. I’m also pretty sure I had been saying it for a while too.
Oh well. Oops, I guess.
This is one of those words that falls right out of my ears the moment I hear it. I’ve looked it up like 20 times now…
Did you somehow get it confused with トウムギ？
That’s what the people in my small town in Miyagi prefecture call corn. Apart from that, I just say コーン. I can’t be bothered to remember ともろこし 
Pretty sure it has a long U as in とうもろこし, anyways
コーン to me is more the not whole already cooked canned one.
There’s no particular reason why my brain got stuck on コウモリ. It just fitted the visual in my mind.
I will entirely own this one. Just pure dumbness haha
Indeed, there is.
See?
Still can’t get it right, dammit! 
Just last week, when I was asking for a plastic bag (forgot my reusable bag) I said “大きい袋です。”. Which, correct me if I’m wrong, should translate as “I’m a big bag”. I can say that I’m just tired from work but I don’t think that’s an excuse haha.
I have been studying Japanese for 3 years now and this is one of my most embarrassing brain farts to date haha.
I almost forgot my worst one! Must have repressed it.
I misread 断食 for a solid few months and just went about my day trying to tell people I was fasting… I, in fact, told them I was doing sodomy
This is going to secondhand haunt me too now oh my god. Who was the poor soul who let you in on the mistake?
Thanks to 男色ディーノ, a wrestler at DDT Pro Wrestling whose gimmick I have very mixed feelings on (he’s gay in real life, but that does not stop his character from being sometimes very problematic…), 男色 was actually one of the first Japanese words I learned after getting into pro wrestling . I guess I should be grateful that I am not in any danger of making that specific mistake, haha.
I cringe at the memory of addressing my 先生 as あなた that one time, I am not worthy of this trial. Last class I forgot how to say cold in Japanese, I am convinced I am too stupid for this. I guess there is not point in getting mad about it. Cannot get mad about the sun rising, amirite?
You can and you should.
The worst part is, no one told me. I found out myself when trying to remember the 断 kanji and typing だんしょく into the dictionary, because then that kanji would certainly show up, right? That’s obviously how to say 断食, right? …right?
Ironically she must have known the word キャンディ because it’s common 外来語. But not associating the two… well let’s just say I hope her nursing skills were better than her basic language skills.
Well you didn’t say the subject so it could mean “this” or “that” is a big bag too.
Or, “what I want” is a big bag.
Almost certainly not my ‘latest’, but the best one to come to mind was sometime last week.
I was writing some instructions on the board for my students, with information about a presentation they’ll be working on. They’re each supposed to speak for one minute during the presentation, so while writing out the directions I decided to put a little 「～1分」next to the description of each students’ part!
…Except I forgot the upper parts of 分 and accidentally wrote 刀 instead. Thankfully the first few students who got to class and I had a quick, mildly confused conversation, and then I fixed my mistake and they all got to laugh at me a bit.
(One katana, one katana, one katana…)
I always joke that my classroom policy is no weapons unless you brought enough for everybody!
I mean, that’d only be twenty katana, I’m sure I can find a shop around here somewhere…
I once gave a cheerful ご苦労様でした to the kitchen staff on the way out of a yakitori place. When they cracked up laughing I went hang on, what did I just say? Very close, brain, but not quite right. I’m sure they knew what I meant…
I did the same mistake with construction workers doing something in the street in front of my place.
I think they laughed because ご苦労様でした is almost only used from superiors to subordinates, so you talked to them like you own the place and they are your employee.