Reason for pointing out quirks?

Ok, was debating whether to post this because I know it sounds like one of those silly teenage questions:

But,

My boyfriend is always mimicking my quirks. If I do something, he will copy it, or pull a silly face to make fun out of me. I don’t know why he does this? I feel he is taking the piss out of me, but he seems to do it in a friendly way.

What is the purpose of this?

( we are in our 30’s and 40’s, although I know it’s wrote young)