beast on
To give someone a hard time undeservedly; to pick on someone.  I hear it used this way 100 times per day in the South Bronx (Hunts Point/Longwood area to be precise. I teach 8th grade there.)
"Terrell, sit down and do the test or you're off to see the dean!"  "Mistuh, you beastin'!  I was just getting up to sharpen my pencil!"