Our team is expanding and our boss hired an agency to find candidates. Today a headhunter on linkedin just offered me this position. Dafuq, at least they could check if I'm not working there on the same position.

Ask what are they offering. Maybe you could get more benefits or salary increase.

Recursive

Happens all the time. I've worked with very few good recruiters.
I'm at a senior level and had a recruiter offer a junior position at less than half of current salary.
Some recruiters are also very unethical. We've had a recruiter place someone with us, only for 6 months later to poach him for somewhere else

I think there was a rant where this happened to the guy that was supposed to interview people. Hilarious