Switch the sheets on your beds while s/he is at class.
Twitch a lot.
Pretend to talk while pretending to be asleep.
Steal a fishtank. Fill it with beer and dump sardines in it. Talk to them.
Become a subgenius.
Inject his/her Twinkles with a mixture of Dexatrim and MSG.
Learn to levitate. While your roommate is looking away, float up out of your seat. When s/he turns to look, fall back down and grin.
Speak in tongues.
Move your roommate's personal effects around. Start subtlety. Gradually work up to big things, and eventually glue everything s/he owns to the ceiling.
Walk and talk backwards.
Spend all your money on Jolt Cola. Drink it all. Stack the cans in the middle of your room. Number them.
Spend all your money on Transformers. Play with them at night. If your roommate says anything, tell him/her with a straight face, "They're more than meets the eye."
Recite entire movie scripts (e.g. The Road Warrior, Repo Man, Casablanca) almost inaudibly.
Kill roaches with a monkey wrench while playing Wagnerian arias on a kazoo. If your roommate complains, explain that it is for your performance art class (or hit him/her with said wrench).
Collect all your urine in a small jug.
Chain yourself to your roommate's bed. Get him/her to bring you food.
Get a computer. Leave it on when you are not using it. Turn it off when you are.
Ask your roommate if your family can move in "just for a couple of weeks."
Buy as many back issues of Field & Stream as you can. Pretend to masturbate while reading them.
Fake a heart attack. When your roommate gets the paramedics to come, pretend nothing happened.
Smoke ballpoint pens.
Smile. All the time.
Collect dog feces in baby food jars. Sort them according to what you think the dog ate.
Burn all your waste paper while eyeing your roommate suspiciously.
Hide a bunch of potato chips and Ho-Hos in the bottom of a trash can. When you get hungry, root around in the trash. Find the food and eat it. If your roommate empties the trash before you get hungry, demand that s/he reimburse you.
Leave a declaration of war on your roommate's desk. Include a list of grievances.
Paste boogers on the windows in occult patterns.
Shoot rubber bands at your roommate while his/her back is turned, and then look away quickly.
Dye all your underwear lime green.
Spill a lot of beer on his/her bed. Swim.
Buy three loaves of stale bread. Grow mold in the closet.
Hide your underwear and socks in your roommate's closet. Accuse him/her of stealing it.
Remove your door. Ship it to your roommate's parents (postage due).
Pray to Azazoth or Zoraster. Sacrifice something nasty.
Whenever your roommate walks in, wait one minute and then stand up. Announce that you are going to shower. Do so. Keep this up for three weeks.
Array thirteen toothbrushes of different colors on your dresser. Refuse to discuss them.
Paint your half of the room black. Or paisley.
Whenever s/he is about to fall asleep, ask questions that start with "Didja ever wonder why...." Be creative.
Shave one eyebrow.
Put your mattress underneath your bed. Sleep down under there and pile your dirty clothes on the empty bedframe. If your roommate comments, mutter "Gotta save space," twenty times while twitching violently.
Put horseradish in your shoes.
Shelve all your books with the spines facing the wall. Complain loudly that you can never find the book that you want.
Always flush the toilet three times.
Subsist entirely on pickles for a week. Vomit often.
Buy a copy of Frankie Yankovic's "Pennsylvania Polka" and play it at least six hours a day. If your roommate complains, explain that it's an assignment for your primitive cultures class.
Give him/her an allowance.
Listen to radio static.
Open your window shades before you go to sleep each night. Close them as soon as you wake up.