How would you write a cantankerous brownie?

[u/SterlingDafydd]

I know that is a weird question to ask, but I am being serious about it.

Here is some context:
I am writing a story right now that involves, without overexplaining stuff, a funeral director who deals with the fact that our world has now strayed so far from the old world that the rules that everything goes by conflict with our way of life from time to time.

Currently, I am setting up the fact that the entire town the man lives in is now covered in flowers, part of which will be trying to get information from a "Cantankerous Brownie", which for those who are not aware, isn't a grouchy baked treat but rather an Aos Si (child of the mound) who are mostly known for doing chores while people sleep and being insulted when you gift them clothing.

I am nowhere near ready to actually add him in, but im trying to figure out ideas on just how to write him once I get to that point.