In what way is "are us" used?
Solution 1:
It's invariably used in fairly lame "witty trading name/slogan" contexts, which as others have pointed out, all derive from the original "Toys R Us". The noun that precedes it is always something "we" (not "us") specialise in supplying.
I can easily imagine someone in a group of enthusiastic drinking buddies saying, for example "Alkies are us!", but after Googling "are us" -shopping and leafing through several pages of results, I have to say it's not exactly a commonplace idiomatic usage outside commercial contexts (that's to say, I didn't come across a single instance of anything 'non-commerical').
Grammatically speaking it's, well, not. You can say, for example, "We are human" in standard English, and "Human are we" in Yoda-speak, but "Human[s] are us" is never going to cut it.
Solution 2:
If you accept the first of the following then the rest follow in a similar pattern:
- It is me
- It is us
- They are us
- Toys are us
So the last is a possible response to the question "Who are toys?" but the shop's name is simply saying "You can buy toys here, as they are what we do."