take naked pictures of yourself put them as your screensaver, make the screensaver password sensitive
leave used tissues (or at least they need to appear that way) around the couch and remote control ensuring to coat the remote in something sticky
apologize for mistakenly using their toothbrush
fart and demand your roommate say 'excuse me'
brag incessantly about simple accomplishments, "oh, yeah! I tied my shoe." "oh, yeah! i turned my computer on." "oh, yeah! I found my pencil"
put mayonnaise on your pepperoni pizza, heat in microwave, sprinkle on garlic, enjoy....talk with husky voice for the rest of the day.