Translation:My dog sells hats.
Had to double take on seeing this one. It is an odd concept, but there is nothing grammatically wrong with it is there? Personally I think it is a good way to check we are actually reading what is there and not what we think should be there. Assuming the sentence is correct.
Now anyone for hat shops for dogs. I mean they already have cat cafes in Japan.
There are many videos of that famous shiba inu which runs (ran) the cigarette shop. The video by Kanadajin3 is likely the one people have seen, however it's hard (not impossible) to find that one online anymore...
The following video of it is my favourite:
I recommend anyone wanting to see the dog running the shop watch this one. It has a good amount of simple Japanese dialogue, making it also great for listening practice. You can hear a lot of the vocabulary taught in this Duolingo course being used in it. ^^
The debates about whether this sentence should or shouldn't be used are interesting because they underscore a deeper issue, ie our perception of language - is language learning a process of primarily memorization or creation? I think there is a lot of evidence that it is both, but second language acquisition linguists still battle hard about it.
Personally, I'm ok with this expression in a 'course' because:
1) It reinforces high frequency words (ie hats, sells, dogs) that I know, but need again 2) It is a reasonable SVO grammar structure for this level (no difficult clauses) 3) I'm not trying to only memorize functional phrases - I want the tools to create language as well. We can play with this sentence with substitutions to make it more functional. (eg My friend sells hats, my dog eats hats, etc...)
Where I think you might want to get after Duo is if you feel the course is introducing structures or words you are just not ready for and demotivating you. I have found this happening on a few occasions, not so much with the Japanese course but more on the Korean one. There you find sentences that are reasonable for communicative purposes but just seem to be something I could say in an easier way or say when I had the means to engage in deeper conversations with Koreans.
You might argue that putting in semantically odd sentences are demotivating because you can't forsee using them but I wonder if it isn't a bit too demanding to expect a free app to be able to balance functionality, level appropriateness, transition and learner motivation perfectly. Perhaps someone just wanted to have a bit of fun with this sentence.