Put some sticky and slimy toothpaste on the toilet seat.

Jam a couple of boullion cubes inside of a shower head. Once water shoots out, your victim will be taking a broth bath.

You can physically remove the toilet seat from any bathroom.

Take the lid off the cistern of a toilet. This is where the part that control the flushing is located. Then pour in some bubble bath liquid and some pink food coloring. The next person to flush the toilet will get pink bubbles everywhere!

Before a group of friends come over, just take a camera into your bathroom and video tape the sink and toilet. As soon as one of your buddies goes to use the toilet, have your other friends gather around the TV, pop in the video you filmed earlier. When your victim comes out of the bathroom he will wonder what everyone is watching and laughing about...he will then see the screen...it will look like he was being videotaped while using the bathroom!!

Pour some vinegar inside your victim's mouthwash.

Place a candle a little below the seat and off to the side. Methane lights up quite nicely.

Place several packages of "Knox" (clear geletin) in the toilet of someone who will not be around for several days. Looks like water and is harder to detect than the celophane on the lid. For a more instant effect, there is a substance availlable at most magic supply stores called anhydrous sodium poly-acrylate which holds up to 300 times its weight in water. Doesn't take much to turn a toilet solid or someone's drink, or...

Shoe Polish of the appropriate color on the toilet seat.

Swipe a person's cloths while they are showering. Put them in an embarasing place such as the showers for people of the opposite sex.

Write "Out Of Order" on a sticker note or piece of paper and tape it to the outside of a bathroom stall. Some people will think there is something wrong with the toilet and avoid using it.

Crack a couple of eggs and drop them in the soap dispenser. Whoever washes their hands next will try to wash their hands with eggs.

Place a small tube in one or the water holes with the other end pointed outward at the victim. When flushed results in an improptu shower.

Go into the school bathroom and remove the top toilet lid. Look for a rubber thin pipe on the side, and disconnect that pipe. You will see a little hair barrette like thing connecting the rubber pipe to the plastic pipe. The next person that flushes the toilet will get a gush shooting upwards.

Leave toothpast on the underside of light switches and doorknobs.