I used to work for the federal government and we all HATED a certain department manager. It was a huge facility with hundreds of employees and had an institutional sized break room with several glass door commercial refrigerators, like you see at convenience stores. Employees had to have their names on all refrigerated items or they would be thrown out. Somehow I wound up with a bottle of chocolate flavored edible lube, so I put the department manager's name on it and stuck it amongst the bottles of condiments. The department manager was too good to eat in the break room with the peons, so she never saw it. Everybody hated her and got a huge laugh out of it and the chocolate lube sat in the fridge for months :) Maybe put something like that randomly in their refrigerator or in a cabinet.