Username has your username in it.. Matt looks like your coffee cat.. and happens to like coffee.. coincidence? I think not~ But likely not worth going after them about it unless they try to claim art that isn't theirs too.

One thing I will say is that though this is a blatant copy/paste, It's best we try to remain civilized about this. Imitation is the sincerest form of flattery after all.

Also, though it probably doesn't apply here, A small artist (well, commissioner) was being called out by a considerably bigger artist for allegedly stealing their OC design. Though both designs were very similar, it was just sheer coincidence and the incident blew over (to my knowledge). Just something to keep in mind if you believe an OCs being stolen.

You should confront him and slapped him with a CopyCat Yu-Gi-Oh card. XD

Some people really lack original thought
It’s one thing to be inspired by a character, or to even copy a couple traits you like, but to take the whole character and claim it as an original thought or design is pretty sad. I’m sure at the very least, they’ll come to understand that some day and feel embarrassment/shame over it and learn to grow as a person.

This person is from Argentina, I'm from Argentina too, if you want I can try to communicate this on the furry Argentina page...

Oh no I went to their page and now they watched me on deviantart xD

If imitation is the sincerest form of flattery...

...he must really like you -w-