Had a kind, polite Japanese housemate in 2002. Her western boyfriend was an egotistical prick with a screw loose who made me feel unwelcome in my own home and unofficially moved in behind my back helping himself to the food in my cupboard. One morning around 2.30am he buzzed our downstairs intercom and started pestering her. She was greatly upset by this and told him to go away. I tried to tell him the same when I offered to talk to him. “Who the BEEP are you?” he asked.
“I’m her housemate. Please go. You’re upsetting her.”
“Who the BEEP do you think you are?”
“*I’M* the guy calling the cops!”
And I did. The little weasel disappeared from the scene when they came around.
(Later, he was pretty much stalking her and she had to leave. But at least I stood my ground)

And YOU?