For goodness sakes, just STOP JOKING AROUND.

Try to be as professional as possible and ignore trying to fit in. Your attempts to do so are ending in failure. Why continually risk that? Just do your job. Leave the inappropriate behaviour to others and don't even consider playing that game. By being careful about your own actions you will increase your chances of (1) gaining the respect of your co-workers; and (2) making a success of your work. Concentrate on your work only. Instead of joining in, report the inappropriate behaviour to your case worker.

Joking around is never appropriate in a workplace. Instead of trying to figure out how to play the game just don't participate in it at all.